New WWAN subsystem support for MM 1.16

Merged Aleksander Morgado requested to merge aleksm/ModemManager:aleksander/wwan-1-16 into mm-1-16

The new Linux WWAN subsystem exposes the various WWAN control ports as character devices. WWAN port device naming follows the following convention: wwanXpYP, where X is the wwan device index, Y the port index and P the port type/protocol.

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