drm/v3d/v3d_gem: Provide descriptions for 'v3d_lookup_bos's params

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

 drivers/gpu/drm/v3d/v3d_gem.c:292: warning: Function parameter or member 'bo_handles' not described in 'v3d_lookup_bos'
 drivers/gpu/drm/v3d/v3d_gem.c:292: warning: Function parameter or member 'bo_count' not described in 'v3d_lookup_bos'

Cc: Eric Anholt <eric@anholt.net>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
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: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201116174112.1833368-36-lee.jones@linaro.org