compositor: make keep_buffer a bool

The comments already call it bool, so let's just make it one

Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/compositor-drm.c

@@ -1106,9 +1106,9 @@ drm_assign_planes(struct weston_output *output)
 		    (es->buffer_ref.buffer &&
 		    (!wl_shm_buffer_get(es->buffer_ref.buffer->resource) ||
 		     (ev->surface->width <= 64 && ev->surface->height <= 64))))
-			es->keep_buffer = 1;
+			es->keep_buffer = true;
 		else
-			es->keep_buffer = 0;
+			es->keep_buffer = false;
 
 		pixman_region32_init(&surface_overlap);
 		pixman_region32_intersect(&surface_overlap, &overlap,

src/compositor.h

@@ -880,7 +880,7 @@ struct weston_surface {
 	struct weston_buffer_viewport buffer_viewport;
 	int32_t width_from_buffer; /* before applying viewport */
 	int32_t height_from_buffer;
-	int keep_buffer; /* bool for backends to prevent early release */
+	bool keep_buffer; /* for backends to prevent early release */
 
 	/* wl_viewport resource for this surface */
 	struct wl_resource *viewport_resource;