[chirp_devel] [patch] initial support for AnyTone 778uv

Hello,

As a bit of lockdown fun I've written a driver for the AnyTone 778UV, see issue #4901. It only supports memories (no settings) and can control frequency, offset, duplex, power level, and CTCSS tones.

Testing so far has been pretty limited, it passes the chirp test suite, and I can round-trip settings from chirp to the radio to the AnyTone software and back without corruption.

Patch and factory image attached. It's my first chirp driver, so I'm sure there will be things to change. Suggestions welcome.

Cheers Joe