-DTR and -RTS Lines do not reset when releasing PTT

[IvanGirderboot]

When using direct serial for PTT, the -DTR and -RTS lines do not properly return HIGH when PTT is released. This causes the connected radio to keep transmitting indefinitely until QSSTV is closed.

[IvanGirderboot]

Compiled and tested on a Raspberry Pi 500+ using an AIOC interface cable to a Baofeng 5HR Radio.