Revert "net: add exit_batch_rtnl() method"

This reverts commit 760f415e which is
commit fd4f101e 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: I7cd575ae9e9d99f5181fdc297649d7e9f96d56fc
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>