radeonsi: set CB_COLORn_INFO.SIMPLE_FLOAT

This can help enable some blend optimizations (see the register spec).
Vulkan always sets this.

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>

src/gallium/drivers/radeonsi/si_state.c

@@ -2066,6 +2066,7 @@ static void si_initialize_color_surface(struct si_context *sctx,
 		S_028C70_COMP_SWAP(swap) |
 		S_028C70_BLEND_CLAMP(blend_clamp) |
 		S_028C70_BLEND_BYPASS(blend_bypass) |
+		S_028C70_SIMPLE_FLOAT(1) |
 		S_028C70_NUMBER_TYPE(ntype) |
 		S_028C70_ENDIAN(endian);