freedreno: serialize drmPrimeFDToHandle under table_lock

fixes the prime sharing race condition described by
"intel: Serialize drmPrimeFDToHandle with struct_mutex".

we inline fd_bo_from_handle() into fd_bo_from_dmabuf() and allow locking.

Signed-off-by: Varad Gautam <varadgautam@gmail.com>
Signed-off-by: Rob Clark <robclark@freedesktop.org>