netfilter: xt_time: print timezone for user information

Let users have a way to figure out if their distro set the kernel
timezone at all.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>