wwan: patches for register and connect procedures

[milan-zededa]

This PR contains two patches for LTE connectivity:

wwan: Explicitly request IPv4 connection

Without explicitly asking for IPv4 (which we only support for wwan), for some LTE networks the connect request may fail with:

error: couldn't start network: QMI protocol error (14): 'CallFailed'
call end reason (1): generic-unspecified
verbose call end reason (6,50): [3gpp] ipv4-only-allowed

This error is returned by network to indicate that only PDN type IPv4 is allowed for the requested PDN connectivity (which is want we want but we need to be explicit about it).

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wwan: make sure we are registering to network with the right APN

Some LTE networks require explicit (and correct) APN for the registration/attach procedure (for the initial EPS bearer activation).