chore(thorvg): fix warning

[FASTSHIFT]

Description of the feature or fix

CC:  In file included from lvgl/lvgl/src/draw/sw/lv_draw_sw.c:22:
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:436:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  436 | TVG_API Tvg_Canvas* tvg_swcanvas_create();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1040:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1040 | TVG_API Tvg_Paint* tvg_shape_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1715:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1715 | TVG_API Tvg_Gradient* tvg_linear_gradient_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1737:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1737 | TVG_API Tvg_Gradient* tvg_radial_gradient_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1959:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1959 | TVG_API Tvg_Paint* tvg_picture_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:2066:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 2066 | TVG_API Tvg_Paint* tvg_scene_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:2144:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 2144 | TVG_API Tvg_Saver* tvg_saver_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:2226:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 2226 | TVG_API Tvg_Animation* tvg_animation_new();
      | ^~~~~~~
CC:  lvgl/lvgl/src/draw/vg_lite/lv_draw_vg_lite_arc.c In file included from lvgl/lvgl/src/draw/sw/lv_draw_sw_vector.c:15:
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:436:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  436 | TVG_API Tvg_Canvas* tvg_swcanvas_create();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1040:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1040 | TVG_API Tvg_Paint* tvg_shape_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1715:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1715 | TVG_API Tvg_Gradient* tvg_linear_gradient_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1737:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1737 | TVG_API Tvg_Gradient* tvg_radial_gradient_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:1959:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 1959 | TVG_API Tvg_Paint* tvg_picture_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:2066:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 2066 | TVG_API Tvg_Paint* tvg_scene_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:2144:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 2144 | TVG_API Tvg_Saver* tvg_saver_new();
      | ^~~~~~~
lvgl/lvgl/src/draw/sw/../../libs/thorvg/thorvg_capi.h:2226:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 2226 | TVG_API Tvg_Animation* tvg_animation_new();
      | ^~~~~~~

Notes

• Update the Documentation if needed.
• Add Examples if relevant.
• Add Tests if applicable.
• If you added new options to lv_conf_template.h run lv_conf_internal_gen.py and update Kconfig.
• Run scripts/code-format.py (astyle needs to be installed) and follow the Code Conventions
• Mark the Pull request as Draft while you are working on the first version, and mark is as Ready when it's ready for review.
• When changes were requested, re-request review to notify the maintainers.
• Help us to review this Pull Request! Anyone can approve or request changes.

[C47D]

LGTM