docs: trusted-encryped: add PKWM as a new trust source

docs: trusted-encryped: add PKWM as a new trust source

Update Documentation/security/keys/trusted-encrypted.rst and Documentation/
admin-guide/kernel-parameters.txt with PowerVM Key Wrapping Module (PKWM)
as a new trust source

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
Tested-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260127145228.48320-7-ssrish@linux.ibm.com