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

In the Linux kernel, the following vulnerability has been resolved: 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)