xen/arm: Release IRQ routed to a domain when it's destroying

xen/arm: Release IRQ routed to a domain when it's destroying

Xen has to release IRQ routed to a domain in order to reuse later.
Currently only SPIs can be routed to the guest so we only need to
browse SPIs for a specific domain.

Furthermore, a guest can crash and leave the IRQ in an incorrect state
(i.e has not been EOIed). Xen will have to reset the IRQ in order to
be able to reuse the IRQ later.

Introduce 2 new functions for release an IRQ routed to a domain:
    - release_guest_irq: upper level to retrieve the IRQ, call the GIC
    code and release the action
    - gic_remove_guest_irq: Check if we can remove the IRQ, and reset
    it if necessary

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>