dm crypt: fix get_key_size compiler warning if !CONFIG_KEYS

stable inclusion
from stable-v5.10.110
commit 5349cde1dfaae67554fec4e844ef9c0030a0dd87
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5349cde1dfaae67554fec4e844ef9c0030a0dd87

--------------------------------

[ Upstream commit 6fc51504 ]

Explicitly convert unsigned int in the right of the conditional
expression to int to match the left side operand and the return type,
fixing the following compiler warning:

drivers/md/dm-crypt.c:2593:43: warning: signed and unsigned
type in conditional expression [-Wsign-compare]

Fixes: c538f6ec ("dm crypt: add ability to use keys from the kernel key retention service")
Signed-off-by: NAashish Sharma <shraash@google.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/md/dm-crypt.c

@@ -2561,7 +2561,7 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string
 
 static int get_key_size(char **key_string)
 {
-	return (*key_string[0] == ':') ? -EINVAL : strlen(*key_string) >> 1;
+	return (*key_string[0] == ':') ? -EINVAL : (int)(strlen(*key_string) >> 1);
 }
 
 #endif /* CONFIG_KEYS */