vxlan: do not output confusing error message

The message "Cannot bind port X, err=Y" creates only confusion. In metadata
based mode, failure of IPv6 socket creation is okay if IPv6 is disabled and
no error message should be printed. But when IPv6 tunnel was requested, such
failure is fatal. The vxlan_socket_create does not know when the error is
harmless and when it's not.

Instead of passing such information down to vxlan_socket_create, remove the
message completely. It's not useful. We propagate the error code up to the
user space and the port number comes from the user space. There's nothing in
the message that the process creating vxlan interface does not know.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>