linux-imx

drm/atomic-helper: Fix kerneldoc for prepare_planes

Copypaste-fail from cleanup_planes. Reported by Tvrtko.

Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>