xen/arm: Implement hypercall DOMCTL_{, un}bind_pt_pirq

xen/arm: Implement hypercall DOMCTL_{, un}bind_pt_pirq

On x86, an IRQ is assigned in 2 steps to an HVM guest:
    - The toolstack is calling PHYSDEVOP_map_pirq in order to create a
    guest PIRQ (IRQ bound to an event channel)
    - The emulator (QEMU) is calling DOMCTL_bind_pt_irq in order to
    bind the IRQ

On ARM, there is no concept of PIRQ as the IRQ can be assigned to a
virtual IRQ using the interrupt controller.

It's not clear if we will need 2 different hypercalls on ARM to assign
IRQ and, for now, only the toolstack will manage IRQ.

In order to avoid re-using a fixed ABI hypercall (PHYSDEVOP_*) for a
different purpose and allow us more time to figure out the right out,
only DOMCTL_{,un}bind_pt_pirq is implemented on ARM.

The DOMCTL is extended with a new type PT_IRQ_TYPE_SPI and only IRQ ==
vIRQ (i.e machine_irq == spi) is supported.

In order to keep the same XSM checks done by the 2 hypercalls on x86,
call both xsm_map_domain_irq & xsm_bind_pt_irq in the ARM implementation.

Note: The toolstack changes for routing an IRQ to a guest will be done
in a separate patch.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Cc: Jan Beulich <jbeulich@suse.com>