drm/msm: Split submit_lookup_objects() into two loops

First loop does copy_from_user() without the table lock held and
just stores the handle. Second loop looks up buffer objects with the
table_lock held without potentially blocking or faulting. This lets us
clean up a bunch of custom, non-faulting copy_from_user() code.

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