powerpc/xmon: Improve output of XIVE interrupts

When looping on the list of interrupts, add the current value of the
PQ bits with a load on the ESB page. This has the side effect of
faulting the ESB page of all interrupts.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190910081850.26038-2-clg@kaod.org