Revert "compositor-drm: disable hardware cursors"

This reverts commit 6858383d51.

The main reason for the original patch was a regression on the Intel
drivers causing compositor framerate to drop to half during cursor
updates or motion. The Intel problem was fixed in
2e7f43c41c
The fix is included in Linux 4.1-rc6 and 4.0.5.

The comment in the original patch is still true, but arguably the
possible minor glitches with cursor updates are less bad than not using
cursor planes at all.

Cc: nerdopolis <bluescreen_avenger@verizon.net>
Cc: Daniel Stone <daniel@fooishbar.org>
Cc: Giulio Camuffo <giuliocamuffo@gmail.com>
Cc: David FORT <contact@hardening-consulting.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Tested-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

src/compositor-drm.c

@@ -3075,12 +3075,12 @@ drm_backend_create(struct weston_compositor *compositor,
 	 * without nuclear page flip. Without nuclear/atomic, hw plane
 	 * and cursor plane updates would either tear or cause extra
 	 * waits for vblanks which means dropping the compositor framerate
-	 * to a fraction.
+	 * to a fraction. For cursors, it's not so bad, so they are
+	 * enabled.
 	 *
 	 * These can be enabled again when nuclear/atomic support lands.
 	 */
 	b->sprites_are_broken = 1;
-	b->cursors_are_broken = 1;
 	b->compositor = compositor;
 
 	section = weston_config_get_section(config, "core", NULL, NULL);