powerpc/xmon: Add source flags to output of XIVE interrupts

Some firmwares or hypervisors can advertise different source
characteristics. Track their value under XMON. What we are mostly
interested in is the StoreEOI flag.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200306150143.5551-4-clg@kaod.org