drivers: nhs_ser: do not force CRTSCTS (breaks CDC-ACM and 3-wire serial)

Forcing CRTSCTS in openfd() blocks communication on NHS UPSes whose port
     has no hardware flow-control lines: USB/CDC-ACM virtual ports (e.g.
     /dev/ttyACM0) and the official NHS 3-wire RS-232 cable (DB9 pins 2/3/5
     only, no RTS/CTS). The driver opens the port but never assembles a packet.
     Disabling CRTSCTS restores communication.

Author: jpastoreli

drivers/nhs_ser.c

@@ -595,7 +595,7 @@ static int openfd(const char * portarg, int BAUDRATE) {
 	tty.c_cflag |= CS8;		/* 8 bits per byte */
 
 	/* CTS / RTS */
-	tty.c_cflag |= CRTSCTS;	/* Enable hardware flow control */
+    tty.c_cflag &= ~CRTSCTS;	/* NHS serial / CDC-ACM has no RTS/CTS flow control */
 
 	/* Enable Read and disable modem control */
 	/* // tty.c_cflag |= (CLOCAL | CREAD); */