lib: s390x: sie: Improve validity handling and make it vm specific

The current library doesn't support running multiple vms at once as it
stores the validity once and not per vm. Let's move the validity
handling into the vm and introduce a new function to retrieve the vir.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-Id: <20221021063902.10878-4-frankja@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>