This reverts commit 020eb3da.

Gabriel C reports that it causes his machine to not boot, and we haven't
tracked down the reason for it yet.  Since the bug it fixes has been
around for a longish time, we're better off reverting the fix for now.

Gabriel says:
 "It hangs early and freezes with a lot RCU warnings.

  I bisected it down to :

  > Ruslan Ruslichenko (1):
  >       x86/ioapic: Restore IO-APIC irq_chip retrigger callback

  Reverting this one fixes the problem for me..

  The box is a PRIMERGY TX200 S5 , 2 socket , 2 x E5520 CPU(s) installed"

and Ruslan and Thomas are currently stumped.
Reported-and-bisected-by: Gabriel C <nix.or.die@gmail.com>
Cc: Ruslan Ruslichenko <rruslich@cisco.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org   # for the backport of the original commit
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>