Revert "net: vxlan: use kfree_skb_reason() in vxlan_mdb_xmit()"

This reverts commit 6fa0469b which is
commit 03483dbd 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: If041063ca818738ed0bf5dbbc62ed89592edd740
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>