crypto: ux500 - Fix kmap() bug

Once the crypto hash walk is started by crypto_hash_walk_first()
returning non-zero, crypto_hash_walk_done() must be called to unmap any
memory which was mapped by *_walk_first().

Ensure crypto_hash_walk_done() is called properly by:

	1) Re-arranging the check for device data to be prior to calling
	   *_walk_first()
	2) on error call crypto_hash_walk_done() with an error code to
	   allow the hash walk code to clean up.

While we are at it clean up the 'out' label to be more meaningful.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>