Sparseirq got introduced in v2.6.28 and Thomas did a huge cleanup
around v2.6.38 that eliminated basically all disadvantages
of it.

So we can remove non-sparseirq support now and simplify
our IRQ degrees of freedom a bit.
Suggested-and-acked-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/4E95E21D.6090200@oracle.comSigned-off-by: NIngo Molnar <mingo@elte.hu>