[SPARC64]: Kill ino_bucket->pil

And reuse that struct member for virt_irq, which will
be used in future changesets for the implementation of
mapping between real and virtual IRQ numbers.

This nicely kills off a ton of SBUS and PCI controller
PIL assignment code which is no longer necessary.

Signed-off-by: David S. Miller <davem@davemloft.net>