ppc/xive: Fix pulling pool and phys contexts

ppc/xive: Fix pulling pool and phys contexts

This improves the implementation of pulling pool and phys contexts in
XIVE1, by following closer the OS pulling code.

In particular, the old ring data is returned rather than the modified,
and irq signals are reset on pull.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Glenn Miles <milesg@linux.ibm.com>
Reviewed-by: Michael Kowal <kowal@linux.ibm.com>
Reviewed-by: Caleb Schlossin <calebs@linux.ibm.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20250512031100.439842-17-npiggin@gmail.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>