Add a way to disable the timer IRQ routing check via a boot option.  The
VMI timer code uses this to avoid triggering the pester Mingo code, which
probes for some very unusual and broken motherboard routings.  It fires
100% of the time when using a paravirtual delay mechanism instead of using
a realtime delay, since there is no elapsed real time, and the 4 timer IRQs
have not yet been delivered.

In addition, it is entirely possible, though improbable, that this bug
could surface on real hardware which picks a particularly bad time to enter
SMM mode, causing a long latency during one of the timer IRQs.

While here, make check_timer be __init.
Signed-off-by: NZachary Amsden <zach@vmware.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
[chrisw: use no_timer_check to bring inline with x86_64 as per Andi's request]
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>