radeonsi: drop useless memcmp() check in si_set_blend_color()

cso_set_blend_color() already checks if the old state is different.
Only Nine uses pipe::set_blend_color() directly but I guess it
should use the cache too.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/drivers/radeonsi/si_state.c

@@ -619,9 +619,6 @@ static void si_set_blend_color(struct pipe_context *ctx,
 {
 	struct si_context *sctx = (struct si_context *)ctx;
 
-	if (memcmp(&sctx->blend_color.state, state, sizeof(*state)) == 0)
-		return;
-
 	sctx->blend_color.state = *state;
 	si_mark_atom_dirty(sctx, &sctx->blend_color.atom);
 }