The common class doesn't change, the KVM one is sPAPR specific. Rename
variables and functions to xics_spapr.

Retain the type name as "xics" to preserve migration for existing sPAPR
guests.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NNikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>