[PATCH] x86_64: Don't need to read PIT in timer handler when PM timer is used

The PM timer path through main_timer_handler doesn't need
the delay variable because it figures it out in a different way.
Don't try to read it from the PIT. With stopped PIT timer
it is even useless.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>