Fix serprog on FreeBSD

Using serprog on FreeBSD to read an SPI flash (MX25L6406) via an
Arduino Nano V3 with flashrom hangs after 5 seconds while reading. The
problem is that kernel method "ttydisc_rint" ignores some bytes. It
happens due to enabled IEXTEN local flag of termios. TTY cuts a few
bytes, Arduino reads 11264 bytes, but flashrom gets only 11244 bytes
and waits for the remaining 20 bytes.

The fix is simple: turn off the IEXTEN local flag.

Tested on Arduino Nano V3 + FreeBSD 12-CURRENT.

Change-Id: I7aa6a283d523c544d9b8923cd4c622bf08c0fb3f
Signed-off-by: Michael Zhilin <mizhka@gmail.com>
Reviewed-on: https://review.coreboot.org/21919
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Urja Rannikko <urjaman@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/serial.c b/serial.c
index 608464b..aa75708 100644
--- a/serial.c
+++ b/serial.c
@@ -215,7 +215,7 @@
 	}
 	wanted.c_cflag &= ~(PARENB | CSTOPB | CSIZE | CRTSCTS);
 	wanted.c_cflag |= (CS8 | CLOCAL | CREAD);
-	wanted.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
+	wanted.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG | IEXTEN);
 	wanted.c_iflag &= ~(IXON | IXOFF | IXANY | ICRNL | IGNCR | INLCR);
 	wanted.c_oflag &= ~OPOST;
 	if (tcsetattr(fd, TCSANOW, &wanted) != 0) {