[PATCH] x86-64: Simplify the vector allocator.

There is no reason to remember a per cpu position of which vector
to try.  Keeping a global position is simpler and more likely to
result in a global vector allocation even if I don't need or require
it.  For level triggered interrupts this means we are less likely to
acknowledge another cpus irq, and cause the level triggered irq to
harmlessly refire.

This simplification makes it easier to only access data structures
of  online cpus, by having fewer special cases to deal with.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andi Kleen <ak@suse.de>