gas: Expose the "Mode" TLV in "DMS Get Firmware List" output as an enum type
This is actually a QmiGasFirmwareListingMode, so let's reflect that in the API. Also rename it to "Mode" so it matches the input.
This is actually a QmiGasFirmwareListingMode, so let's reflect that in the API. Also rename it to "Mode" so it matches the input.