serial: use internal_delay() for timeouts

Using programmer_delay() for timeouts in serial writes could cause a
(theoretically) endless recursion if serial communication is used to
send the programmer the delay command to be executed on the programmer
instead of the host which fails again, following a timeout which
sends...

Corresponding to flashrom svn r1759.
Signed-off-by: Urja Rannikko <urjaman@gmail.com>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>

serial.c

@@ -357,7 +357,7 @@ int serialport_write(unsigned char *buf, unsigned int writecnt)
 		if (!tmp) {
 			msg_pdbg2("Empty write\n");
 			empty_writes--;
-			programmer_delay(500);
+			internal_delay(500);
 			if (empty_writes == 0) {
 				msg_perr("Serial port is unresponsive!\n");
 				return 1;