tools: kwboot: Show 'E' in progress output when error occurs

When kwboot is unable to resend current xmodem packet, show an 'E' in the
progress output instead of a '+'. This allows to distinguish between the
state when kwboot is retrying sending the packet and when retry is not
possible.

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 dfac8ae..1dcec19 100644
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -975,8 +975,12 @@
 		if (rc)
 			goto err;
 
-		if (!allow_non_xm && c != ACK)
-			kwboot_progress(-1, '+');
+		if (!allow_non_xm && c != ACK) {
+			if (c == NAK && allow_retries && retries + 1 < 16)
+				kwboot_progress(-1, '+');
+			else
+				kwboot_progress(-1, 'E');
+		}
 	} while (c == NAK && allow_retries && retries++ < 16);
 
 	if (non_xm_print)