meson: also expose present_sync for VT-only after a96d04f

$ meson setup --auto-features=disabled -Ddrm=enabled -Degl=enabled -Dgbm=enabled -Degl-drm=enabled /tmp/mpv_build
$ meson compile -C /tmp/mpv_build
[...]
ld: error: undefined symbol: mp_present_initialize
>>> referenced by drm_common.c
>>>               libmpv.so.2.2.0.p/video_out_drm_common.c.o:(vo_drm_init)

ld: error: undefined symbol: present_sync_update_values
>>> referenced by drm_common.c
>>>               libmpv.so.2.2.0.p/video_out_drm_common.c.o:(drm_pflip_cb)

ld: error: undefined symbol: present_sync_swap
>>> referenced by drm_common.c
>>>               libmpv.so.2.2.0.p/video_out_drm_common.c.o:(drm_pflip_cb)

ld: error: undefined symbol: present_sync_get_info
>>> referenced by vo_drm.c
>>>               libmpv.so.2.2.0.p/video_out_vo_drm.c.o:(get_vsync)

meson.build

@@ -1049,7 +1049,7 @@ if features['xv']
     sources += files('video/out/vo_xv.c')
 endif
 
-if features['wayland'] or features['x11']
+if features['wayland'] or features['x11'] or features['drm']
     sources += ('video/out/present_sync.c')
 endif