render/allocator/drm_dumb: get format info before allocating

Simplifies error handling a bit.

render/allocator/drm_dumb.c

@@ -55,20 +55,20 @@ static struct wlr_drm_dumb_buffer *create_buffer(
 		return NULL;
 	}
 
-	struct wlr_drm_dumb_buffer *buffer = calloc(1, sizeof(*buffer));
-	if (buffer == NULL) {
-		return NULL;
-	}
-	wlr_buffer_init(&buffer->base, &buffer_impl, width, height);
-	wl_list_insert(&alloc->buffers, &buffer->link);
-
 	const struct wlr_pixel_format_info *info =
 		drm_get_pixel_format_info(format->format);
 	if (info == NULL) {
 		wlr_log(WLR_ERROR, "DRM format 0x%"PRIX32" not supported",
 			format->format);
-		goto create_err;
+		return NULL;
+	}
+
+	struct wlr_drm_dumb_buffer *buffer = calloc(1, sizeof(*buffer));
+	if (buffer == NULL) {
+		return NULL;
 	}
+	wlr_buffer_init(&buffer->base, &buffer_impl, width, height);
+	wl_list_insert(&alloc->buffers, &buffer->link);
 
 	struct drm_mode_create_dumb create = {0};
 	create.width = (uint32_t)width;