staging/android: remove driver_data from struct sync_fence_info

It is unclear in what situations driver_data should be used thus better do
not upstream it for now. If a need arises in the future a discussion can
be started to re-add it.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>