s390/crypto: Fix unsigned variable compared with zero

s390_crypto_shash_parmsize() return type is int, it
should not be stored in a unsigned variable, which
compared with zero.
Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 3c2eb6b7 ("s390/crypto: Support for SHA3 via CPACF (MSA6)")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Joerg Schmidbauer <jschmidb@linux.vnet.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/crypto/sha_common.c

@@ -74,14 +74,17 @@ int s390_sha_final(struct shash_desc *desc, u8 *out)
 	struct s390_sha_ctx *ctx = shash_desc_ctx(desc);
 	unsigned int bsize = crypto_shash_blocksize(desc->tfm);
 	u64 bits;
-	unsigned int n, mbl_offset;
+	unsigned int n;
+	int mbl_offset;
 
 	n = ctx->count % bsize;
 	bits = ctx->count * 8;
-	mbl_offset = s390_crypto_shash_parmsize(ctx->func) / sizeof(u32);
+	mbl_offset = s390_crypto_shash_parmsize(ctx->func);
 	if (mbl_offset < 0)
 		return -EINVAL;
 
+	mbl_offset = mbl_offset / sizeof(u32);
+
 	/* set total msg bit length (mbl) in CPACF parmblock */
 	switch (ctx->func) {
 	case CPACF_KLMD_SHA_1: