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>

drivers/crypto/ccree/cc_aead.c

@@ -293,7 +293,8 @@ static unsigned int xcbc_setkey(struct cc_hw_desc *desc,
 	return 4;
 }
 
-static int hmac_setkey(struct cc_hw_desc *desc, struct cc_aead_ctx *ctx)
+static unsigned int hmac_setkey(struct cc_hw_desc *desc,
+				struct cc_aead_ctx *ctx)
 {
 	unsigned int hmac_pad_const[2] = { HMAC_IPAD_CONST, HMAC_OPAD_CONST };
 	unsigned int digest_ofs = 0;