xen/arm: introduce PLATFORM_QUIRK_GUEST_PIRQ_NEED_EOI

xen/arm: introduce PLATFORM_QUIRK_GUEST_PIRQ_NEED_EOI

GICH_LR_HW doesn't work as expected on X-Gene: request maintenance
interrupts and perform EOIs in the hypervisor for hardware interrupts as
a workaround.  Trigger this behaviour with a per platform option.

This patch assumes that GICC_DIR can be written on any pcpu for a given
SPI, not matter where GICC_IAR has been read before.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
CC: psawargaonkar@apm.com
CC: apatel@apm.com