Add warn message if no flash bank found for the current image address.

Add a warn message to inform the user that something is wrong
with the flash settings or command parameters.

Change-Id: Ia55868b2abf2a17845e51620b0f29b2809d841c2
Signed-off-by: Mathias K <kesmtp@freenet.de>
Reviewed-on: http://openocd.zylin.com/280
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/flash/nor/core.c

@@ -595,6 +595,7 @@ int flash_write_unlock(struct target *target, struct image *image,
 		if (retval != ERROR_OK)
 			goto done;
 		if (c == NULL) {
+			LOG_WARNING("no flash bank found for address %x", run_address);
 			section++;	/* and skip it */
 			section_offset = 0;
 			continue;