broadband-modem-mbim: log hex value of IP type if unknown

The L850 seems to report 0xFFFFFFFF as MbimContextIpType value, which
is not a correct value.

Instead of printing "(none)" (the default used by glib when trying to
print a NULL pointer as a string), make it so that we end up printing
the actual numeric value in hex.

   <dbg> [modem0] 'home' settings found at configuration index 0
   <dbg> [modem0] 'non-partner' settings found at configuration index 1
   <dbg> [modem0] 'partner' settings not found
   <dbg> [modem0] updates in the home LTE attach configuration settings:
   <dbg> [modem0]   ip type: 'unknown (0xffffffff)' -> ''ipv4v6'
   <dbg> [modem0] updates in the partner LTE attach configuration settings:
   <dbg> [modem0]   none (skipped)
   <dbg> [modem0] updates in the non-partner LTE attach configuration settings:
   <dbg> [modem0]   none

0 files changed, 0 insertions, 0 deletions