staging/android: remove SYNC_WAIT ioctl

This ioctl is replicating the work of poll() syscall so let's take the
opportunity that this is still on staging tree and remove the duplication
and force new users to use the poll() standard interface.

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