drm/radeon/radeon_ring: Add missing function parameters 'rdev' and 'data'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/radeon/radeon_ring.c:226: warning: Function parameter or member 'rdev' not described in 'radeon_ring_unlock_undo'
 drivers/gpu/drm/radeon/radeon_ring.c:240: warning: Function parameter or member 'rdev' not described in 'radeon_ring_lockup_update'
 drivers/gpu/drm/radeon/radeon_ring.c:283: warning: Function parameter or member 'data' not described in 'radeon_ring_backup'

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_ring.c

@@ -218,6 +218,7 @@ void radeon_ring_undo(struct radeon_ring *ring)
 /**
  * radeon_ring_unlock_undo - reset the wptr and unlock the ring
  *
+ * @rdev:       radeon device structure
  * @ring: radeon_ring structure holding ring information
  *
  * Call radeon_ring_undo() then unlock the ring (all asics).
@@ -231,6 +232,7 @@ void radeon_ring_unlock_undo(struct radeon_device *rdev, struct radeon_ring *rin
 /**
  * radeon_ring_lockup_update - update lockup variables
  *
+ * @rdev:       radeon device structure
  * @ring: radeon_ring structure holding ring information
  *
  * Update the last rptr value and timestamp (all asics).
@@ -275,6 +277,7 @@ bool radeon_ring_test_lockup(struct radeon_device *rdev, struct radeon_ring *rin
  *
  * @rdev: radeon_device pointer
  * @ring: the ring we want to back up
+ * @data: placeholder for returned commit data
  *
  * Saves all unprocessed commits from a ring, returns the number of dwords saved.
  */