drm: msm: fix possible memory leak in mdp5_crtc_cursor_set()

drm_gem_object_lookup will call drm_gem_object_get inside. So cursor_bo
needs to be put when msm_gem_get_and_pin_iova fails.

Fixes: e172d10a

 ("drm/msm/mdp5: Add hardware cursor support")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Link: https://lore.kernel.org/r/20220509061125.18585-1-hbh25y@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>