tools: kwboot: Remove code for handling CAN byte

It is unknown why handling of CAN byte was added into kwboot tool as
Marvell BootROM does not support CAN byte. It never sends CAN byte to host
and if host sends CAN byte BootROM handles it as an unknown byte.

Remove code for handling and sending CAN bytes from the kwboot tool.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/tools/kwboot.c b/tools/kwboot.c
index be9a751..0b97990 100644
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -63,7 +63,6 @@
 #define EOT	4	/* sender end of block transfer */
 #define ACK	6	/* target block ack */
 #define NAK	21	/* target block negative ack */
-#define CAN	24	/* target/sender transfer cancellation */
 
 #define KWBOOT_XM_BLKSZ	128 /* xmodem block size */
 
@@ -826,7 +825,7 @@
 static int
 _is_xm_reply(char c)
 {
-	return c == ACK || c == NAK || c == CAN;
+	return c == ACK || c == NAK;
 }
 
 static int
@@ -841,9 +840,6 @@
 	case NAK:
 		errno = EBADMSG;
 		break;
-	case CAN:
-		errno = ECANCELED;
-		break;
 	default:
 		errno = EPROTO;
 		break;
@@ -966,7 +962,7 @@
 	do {
 		rc = kwboot_tty_send(fd, block, sizeof(*block), 1);
 		if (rc)
-			return rc;
+			goto err;
 
 		if (allow_non_xm && !*done_print) {
 			kwboot_progress(100, '.');
@@ -979,7 +975,7 @@
 					  allow_non_xm, &non_xm_print,
 					  baudrate, &baud_changed);
 		if (rc)
-			goto can;
+			goto err;
 
 		if (!allow_non_xm && c != ACK)
 			kwboot_progress(-1, '+');
@@ -990,15 +986,13 @@
 
 	if (allow_non_xm && baudrate && !baud_changed) {
 		fprintf(stderr, "Baudrate was not changed\n");
-		rc = -1;
 		errno = EPROTO;
-		goto can;
+		return -1;
 	}
 
 	return _xm_reply_to_error(c);
-can:
+err:
 	err = errno;
-	kwboot_tty_send_char(fd, CAN);
 	kwboot_printv("\n");
 	errno = err;
 	return rc;