Revert "vxlan: Rename FDB Tx lookup function"

This reverts commit 317122c5 which is
commit 5cde39ea 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: I215ba5d9c51d0f0b2f7f3e1b24753de7afe3313f
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>