Removed unused variable "err" and directly return "0"

Reported by coccicheck -
./drivers/crypto/atmel-sha.c:758:5-8: Unneeded variable: "err". Return "0" on line 766
Signed-off-by: Rahul Pathak <rpathak@visteon.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>