Jeff Garzik <jgarzik@pobox.com> points out that this was wrong: we need to
disable local interrupts while holding KM_IRQ0 due to IRQ sharing.

And holding interrupts off during a big PIO opration is expensive, so we only
want to do that if we know the page was highmem.

So revert commit 17fd47abSigned-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>