modem: ublox-sara-r4: implement 'is_supported' socket offload cb

Check if requested socket family, type and protocol are all supported by
the driver, instead of blindly acknowledging every possible variant.

There is explicit support for UDP, TCP and TLS on top of IPv4 and IPv6.
TLS seems to be supported only in 1.2 version, so allow just that
version.

Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>