TYT UV-390 Squelch on DMR channels

[adryd325]

The TYT UV-390 and family use squelch on DMR channels. QDMR seems to reset the squelch every time when writing to the radio to zero. It would be nice if the squelch value was stored in tytExtension or something like that.

[adryd325]

If it helps, I tested with my radio: the squelch setting is at the same location in the codeplug for DMR channels and Analog channels

[hmatuschek]

Implemented it in the tyt-squelch-on-dmr-channels branch. I cannot test it right now, so it would be great if you could. If it works for you, I'll merge it into master.

[adryd325]

I just tested it and it works as expected, both reading from and writing to the radio. Thank you so much!