drm/amd/amdgpu/amdgpu_cs: Add a couple of missing function param descriptions

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

 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c:685: warning: Function parameter or member 'backoff' not described in 'amdgpu_cs_parser_fini'
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c:1655: warning: Function parameter or member 'map' not described in 'amdgpu_cs_find_mapping'

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: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Jerome Glisse <glisse@freedesktop.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c

@@ -676,6 +676,7 @@ static int amdgpu_cs_sync_rings(struct amdgpu_cs_parser *p)
  * cs_parser_fini() - clean parser states
  * @parser:	parser structure holding parsing context.
  * @error:	error number
+ * @backoff:	indicator to backoff the reservation
  *
  * If error is set than unvalidate buffer, otherwise just free memory
  * used by parsing context.
@@ -1644,6 +1645,7 @@ int amdgpu_cs_wait_fences_ioctl(struct drm_device *dev, void *data,
  * @parser: command submission parser context
  * @addr: VM address
  * @bo: resulting BO of the mapping found
+ * @map: Placeholder to return found BO mapping
  *
  * Search the buffer objects in the command submission context for a certain
  * virtual memory address. Returns allocation structure when found, NULL