radeonsi: only apply the SNORM blit workaround to *8_SNORM

Like the comment says. This fixes DCC, which doesn't like blitting RG16
as RGBA8.

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

src/gallium/drivers/radeonsi/si_blit.c

@@ -536,7 +536,7 @@ void si_resource_copy_region(struct pipe_context *ctx,
 		src_force_level = src_level;
 	} else if (!util_blitter_is_copy_supported(sctx->blitter, dst, src) ||
 		   /* also *8_SNORM has precision issues, use UNORM instead */
-		   util_format_is_snorm(src->format)) {
+		   util_format_is_snorm8(src->format)) {
 		if (util_format_is_subsampled_422(src->format)) {
 			src_templ.format = PIPE_FORMAT_R8G8B8A8_UINT;
 			dst_templ.format = PIPE_FORMAT_R8G8B8A8_UINT;