radeonsi: fix bounds check in si_create_vertex_elements

This was triggered by
dEQP-GLES3.functional.vertex_array_objects.all_attributes

Cc: "11.1 11.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/drivers/radeonsi/si_state.c

@@ -3278,7 +3278,7 @@ static void *si_create_vertex_elements(struct pipe_context *ctx,
 	struct si_vertex_element *v = CALLOC_STRUCT(si_vertex_element);
 	int i;
 
-	assert(count < SI_MAX_ATTRIBS);
+	assert(count <= SI_MAX_ATTRIBS);
 	if (!v)
 		return NULL;