rasterizer: fix assembly for WIN64

Second argument of cglobal macro for fill_halfplane in 64-bit mode
should always be 6 to preload all function arguments into registers.
It doesn't matter under *nix as the first 6 arguments are already
in registers according to calling conventions, but under WIN64
it's only the first 4.

libass/x86/rasterizer.asm

@@ -120,7 +120,9 @@ FILL_SOLID_TILE 5,32
     DEF_A_SHIFT %1
 %if ARCH_X86_64 && a_shift
 cglobal fill_halfplane_tile%2, 6,7,9
-%elif ARCH_X86_64 || !PIC
+%elif ARCH_X86_64
+cglobal fill_halfplane_tile%2, 6,7,8
+%elif !PIC
 cglobal fill_halfplane_tile%2, 0,7,8
 %else
 cglobal fill_halfplane_tile%2, 0,7,8, -mmsize