crypto: atmel-aes - fix the keys zeroing on errors

The Atmel AES driver uses memzero_explicit on the keys on error, but the
variable zeroed isn't the right one because of a typo. Fix this by using
the right variable.

Fixes: 89a82ef8 ("crypto: atmel-authenc - add support to authenc(hmac(shaX), Y(aes)) modes")
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>