drm/msm: Use correct drm_gem_object_put() in fail case

We only want to use the _unlocked() variant in the unlocked case.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>