s390/pkey: Use kfree_sensitive() to fix Coccinelle warnings

Replace memzero_explicit() and kfree() with kfree_sensitive() to fix
warnings reported by Coccinelle:

WARNING opportunity for kfree_sensitive/kvfree_sensitive (line 1506)
WARNING opportunity for kfree_sensitive/kvfree_sensitive (line 1643)
WARNING opportunity for kfree_sensitive/kvfree_sensitive (line 1770)

Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Link: https://lore.kernel.org/r/ZjqZkNi_JUJu73Rg@octinomon.home
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

drivers/s390/crypto/pkey_api.c

@@ -1503,8 +1503,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 		rc = pkey_keyblob2pkey(kkey, ktp.keylen, ktp.protkey.protkey,
 				       &ktp.protkey.len, &ktp.protkey.type);
 		pr_debug("%s pkey_keyblob2pkey()=%d\n", __func__, rc);
-		memzero_explicit(kkey, ktp.keylen);
-		kfree(kkey);
+		kfree_sensitive(kkey);
 		if (rc)
 			break;
 		if (copy_to_user(utp, &ktp, sizeof(ktp)))
@@ -1640,8 +1639,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 					&ktp.protkey.type);
 		pr_debug("%s pkey_keyblob2pkey2()=%d\n", __func__, rc);
 		kfree(apqns);
-		memzero_explicit(kkey, ktp.keylen);
-		kfree(kkey);
+		kfree_sensitive(kkey);
 		if (rc)
 			break;
 		if (copy_to_user(utp, &ktp, sizeof(ktp)))
@@ -1767,8 +1765,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 					protkey, &protkeylen, &ktp.pkeytype);
 		pr_debug("%s pkey_keyblob2pkey3()=%d\n", __func__, rc);
 		kfree(apqns);
-		memzero_explicit(kkey, ktp.keylen);
-		kfree(kkey);
+		kfree_sensitive(kkey);
 		if (rc) {
 			kfree(protkey);
 			break;