Revert "vxlan: Add RCU read-side critical sections in the Tx path"

This reverts commit 02bebe7d which is
commit 804b09be 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: I799ee76a32ad1b1300602a0b5198a94632c4cd52
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>