KVM: PPC: Enable IRQFD support for the XICS interrupt controller

This makes it possible to use IRQFDs on platforms that use the XICS
interrupt controller.  To do this we implement kvm_irq_map_gsi() and
kvm_irq_map_chip_pin() in book3s_xics.c, so as to provide a 1-1 mapping
between global interrupt numbers and XICS interrupt source numbers.
For now, all interrupts are mapped as "IRQCHIP" interrupts, and no
MSI support is provided.

This means that kvm_set_irq can now get called with level == 0 or 1
as well as the powerpc-specific values KVM_INTERRUPT_SET,
KVM_INTERRUPT_UNSET and KVM_INTERRUPT_SET_LEVEL.  We change
ics_deliver_irq() to accept all those values, and remove its
report_status argument, as it is always false, given that we don't
support KVM_IRQ_LINE_STATUS.

This also adds support for interrupt ack notifiers to the XICS code
so that the IRQFD resampler functionality can be supported.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>