Revert "net: vxlan: add skb drop reasons to vxlan_rcv()"

This reverts commit b186fb3b which is
commit 4c06d9da 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: I005dd22df8932d6c329218e5021ad9fb1f99859c
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>