net: don't warn in inet diag when IPV6 is disabled

If IPV6 was disabled, then ss command would cause a kernel warning
because the command was attempting to dump IPV6 socket information.
The fix is to just remove the warning.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202249


Fixes: 432490f9 ("net: ip, diag -- Add diag interface for raw sockets")
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>