crypto: ccree - fix comparison of unsigned expression warning

This patch fixes the following warnings:
drivers/crypto/ccree/cc_aead.c:630:5-12: WARNING: Unsigned expression
compared with zero: seq_len > 0

Signed-off-by: Tian Tao <tiantao6@huawei.com>

v2:
change hmac_setkey() return type to unsigned int to fix the warning.
Acked-by: Gilad Ben-Yossef <gilad@benyossef.com>

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>