ubifs: Do not skip hash checking in data nodes

UBIFS bails out early from try_read_node() when it doesn't have to check
the CRC. Still the node hash has to be checked, otherwise wrong data
could be sneaked into the FS. Fix this by not bailing out early and
always checking the node hash.

Fixes: 16a26b20 ("ubifs: authentication: Add hashes to index nodes")
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>