KVM: s390: selftests: Add uc_skey VM test case

Add a test case manipulating s390 storage keys from within the ucontrol
VM.

Storage key instruction (ISKE, SSKE and RRBE) intercepts and
Keyless-subset facility are disabled on first use, where the skeys are
setup by KVM in non ucontrol VMs.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Link: https://lore.kernel.org/r/20241108091620.289406-1-schlameuss@linux.ibm.com


Acked-by: Janosch Frank <frankja@linux.ibm.com>
[frankja@linux.ibm.com: Fixed patch prefix]
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Message-ID: <20241108091620.289406-1-schlameuss@linux.ibm.com>