Ailunce HS2 Firmware V1.1.5–20200820

Change log

1. Change the name of the AUDIIO_SOURCE interface option.
   AUDIO change to MIC.
   DIGI change to USB.
   IQ change to SDR.
2. Allow to change AUDIIO_SOURCE in CW mode.
3. Allow to change IFG value in FM mode.
4. Turn on the standing wave protection function, It will turn off when
   the VSWR threshold is 1. Please set the VSWR threshold after update the
   firmware.
5. Fix known UI issues.