defaultenv/bin/update: fix return values

This patch fixes the return values of the update script.

- Exit with an error of the "_update" script fails.
- Add a "else; true" to the crc check, otherwise the script
  exits with "1".

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

defaultenv/bin/update

@@ -64,7 +64,9 @@ if [ x${mode} != xtftp ] && [ x${mode} != xxmodem ] ; then
 	exit 1
 fi
 
-. /env/bin/_update
+. /env/bin/_update || exit 1
 if [ x${check} = xy ]; then
 	crc32 -f $image -F $part
+else
+	true
 fi