linux: prevent invalid or unsupportable PIRQs from being used

linux: prevent invalid or unsupportable PIRQs from being used

By keeping the respective irq_desc[] entries pointing to no_irq_type,
setup_irq() (and thus request_irq()) will fail for such IRQs. This
matches native behavior, which also only installs ioapic_*_type out of
ioapic_register_intr().

At the same time, make assign_irq_vector() fail not only when Xen
doesn't support the PIRQ, but also if the IRQ requested doesn't fall
in the kernel's PIRQ space.

Signed-off-by: Jan Beulich <jbeulich@novell.com>