[PATCH] x86_64 irq: Use NR_IRQS not NR_IRQ_VECTORS

NR_IRQ_VECTORS is currently a compatiblity define set to NR_IRQs.
This patch updates the users of NR_IRQ_VECTORS to use NR_IRQs instead
so that NR_IRQ_VECTORS can be removed.

There is still shared code with arch/i386 that uses NR_IRQ_VECTORS
so we can't remove the #define just yet :(

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>