POSIX Drivers: Clear disconnected status when closing

This allows us to properly re-open if we were
previously disconnected.

platform/posix/ftdi.cpp

@@ -108,6 +108,7 @@ bool FTDI::close() {
 	while(writeQueue.try_dequeue(flushop)) {}
 
 	closing = false;
+	disconnected = false;
 	return ret;
 }
 

platform/posix/stm32.cpp

@@ -102,6 +102,7 @@ bool STM32::close() {
 		writeThread.join();
 
 	closing = false;
+	disconnected = false;
 
 	int ret = ::close(fd);
 	fd = -1;