Fixes faulty IRQ_NONE value returning by VM86 irq_handler().

The IRQ source is blocked as well until userspace confirms processing.
This should enable to use VM86 code even for level triggered interrupt
sources. 
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>