x86: Skip cpus with apic-ids >= 255 in !x2apic_mode

x86: Skip cpus with apic-ids >= 255 in !x2apic_mode

If the x2apic mode is disabled for reasons like interrupt-remapping
not available etc, then we need to skip the logical cpu bringup of
apic-id's >= 255. Otherwise as the platform is in xapic mode, init/startup
IPI's will consider only the low 8-bits and there is a possibility of
re-sending init/startup IPI's to the logical cpu that is already online.

This will avoid potential reboots/unpredictable behavior etc.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/20111222014632.702932458@sbsiddha-desk.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>