Revert "ACPI: Only use IPI on known broken machines (AMD, Dothan/BaniasPentium M)"

This reverts commit 25496cae

, which
broke bootup on at least Ingo's ThinkPad T60.  Need to figure out
exactly what is wrong before we can re-do the logic.

Requested-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Len Brown <len.brown@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>