HMAC keys can be of any length, and atmel_sha_hmac_key_set() can only
fail due to -ENOMEM.  But atmel_sha_hmac_setkey() incorrectly treated
any error as a "bad key length" error.  Fix it to correctly propagate
the -ENOMEM error code and not set any tfm result flags.

Fixes: 81d8750b ("crypto: atmel-sha - add support to hmac(shaX)")
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>