Request the IRQ after having set everything up.  Otherwise a shared interrupt
at the right time can kill the machine.

Found this with David Woodhouse <dwmw2@infradead.org>'s
debug-shared-irqs.patch.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>