pnv/xive: Update PIPR when updating CPPR

pnv/xive: Update PIPR when updating CPPR

Current code was updating the PIPR inside the xive_tctx_accept() function
instead of the xive_tctx_set_cppr function, which is where the HW would
have it updated.

Moved the update to the xive_tctx_set_cppr function which required
additional support for pool interrupts.

Fixes: cdd4de68edb6 ("ppc/xive: notify the CPU when the interrupt priority is more privileged")
Signed-off-by: Glenn Miles <milesg@linux.vnet.ibm.com>
Signed-off-by: Michael Kowal <kowal@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>