drivers: modem: ublox-sara-r4: fix getaddrinfo

The implementation of offload_getaddrinfo in this driver failed
when the node it was called with was an IP address. This condition
was never detected, and as a consequence a DNS query was done on
the IP address instead of returning it directly.

Also, the port was set first after running the DNS query.
As a consequence, if the IP address would have been returned directly,
this would have been done without a port been set.

Both errors are fixed in this patch.

Signed-off-by: Hans Wilmers <hans@wilmers.no>