ARM: vexpress/ca9: Add interrupt-affinity to the PMU node

Commit 9fd85eb5

 ("ARM: pmu: add support for interrupt-affinity
property") added an optional "interrupt-affinity" property, to specify
the CPU affinity for each SPI listed in the interrupts property.

Without this property, we get this boot warning:

  CPU PMU: Failed to parse <no-node>/interrupt-affinity[0]

This patch adds interrupt-affinity to the PMU node in the
vexpress-v2p-ca9 device tree.

Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>