pseries/plpks: expose PowerVM wrapping features via the sysfs

pseries/plpks: expose PowerVM wrapping features via the sysfs

Starting with Power11, PowerVM supports a new feature called "Key Wrapping"
that protects user secrets by wrapping them using a hypervisor generated
wrapping key. The status of this feature can be read by the
H_PKS_GET_CONFIG HCALL.

Expose the Power LPAR Platform KeyStore (PLPKS) wrapping features config
via the sysfs file /sys/firmware/plpks/config/wrapping_features.

Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
Tested-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260127145228.48320-4-ssrish@linux.ibm.com