Update interrupt handling code to handle mem-free mode.  While we're
at it, improve the Tavor interrupt handling to avoid an extra MMIO
read of the event cause register.
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>