Revert "net: add exit_batch_rtnl() method"

This reverts commit 1e222169 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: I986a520aef6b1fa89f9e5e66deab1e52e8f1b3b6
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>