Empty assistance data from gnss_assistance_get_status

[jbodegraven]

in __handle_lp_gnss_assistance the test

_UNICODE_0 = const(0)

if part_no == 0:
	if part[0] == _UNICODE_0:
		gnss_details = cmd.rsp.gnss_assistance.almanac

Never works because '0' is 48. gnss_details never gets assigned and the objects stay empty.

I've rewritten it like so:

if part_no == 0:
	type_code = int(part)
	if type_code == WalterModemGNSSAssistanceType.ALMANAC:
		gnss_details = cmd.rsp.gnss_assistance.almanac
	elif type_code == WalterModemGNSSAssistanceType.REALTIME_EPHEMERIS:
		gnss_details = cmd.rsp.gnss_assistance.realtime_ephemeris
	elif type_code == WalterModemGNSSAssistanceType.PREDICTED_EPHEMERIS:
		gnss_details = cmd.rsp.gnss_assistance.predicted_ephemeris

Now it works and cmd.rsp.gnss_assistance is properly populated

Also cleaned out the _UNICODE_0 = const(0), etc, because they're no longer used, they are wrong and using the existing enum is a cleaner way of doing it imo.

Do you agree? would you like me to submit a pull request (never done that) ?