When the operator is one of those listed in EF-SPDI then we need to
treat it like a HPLMN in deciding whether the SPN or PLMN name should
be displayed.
Implement basic SIM filesystem utilities.
Obtain Service Provider Name EF-SPN record.
Make NetworkRegistration use SPN for PLMN display. This implements PLMN
display rules in 31.102 "EFSPN".