Revert "gtp: use exit_batch_rtnl() method"

This reverts commit a111a748 which is
commit 6eedda01 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ide4de81bedb34df80d246245b09bcb402cd92c57
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>