PREEMPT_BITS, SOFTIRQ_BITS, PREEMPT_SHIFT, SOFTIRQ_SHIFT and HARDIRQ_SHIFT
are the same for all architectures (and chaning them in future ports
doesn't make a lot of sense), so move them to <linux/hardirq.h>.

Make the HARDIRQ_BITS definition guarded by #ifndef HARDIRQ_BITS instead of
CONFIG_GENERIC_HARDIRQS so we have a saner way to override it once ports
with lots of irq sources are changed to use the generic hardirq framework.

Ingo, maybe we should change the default for it back to 8 as that's what
most ports use?
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>