staging/android/sync: add sync_fence_create_dma

This allows users of dma fences to create a android fence.

v2: Added kerneldoc. (Tvrtko Ursulin).

v4: Updated comments from review feedback my Maarten.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: devel@driverdev.osuosl.org
Cc: Riley Andrews <riandrews@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>