We were simply concatenating the devhandle and devino and using that
as the cookie, which defeats the entire purpose of the VIRQ hypervisor
interfaces.

Now that we use physical addresses for the INO buckets, we can
allocate them dynamically for VIRQs and encode the cookies as
~__pa(bucket).  This allows us to test for and decode the cookie with
a simple:

	brlz	$reg1, 1f
	 xnor	$reg1, %g0, $reg2

sequence.

This works because bit 64 is never set in traditional
INO vectors, and it is also never set in a physical
address.  So xnor'ing the physical address of the bucket
always gives us a negative number, and thus a unique
condition we can test cheaply.

Inspired by ideas from Greg Onufer.
Signed-off-by: David S. Miller <davem@davemloft.net>