x86, apic: Make disabled_cpu_apicid static read_mostly, fix typos

Make disabled_cpu_apicid static and read_mostly, and fix a couple of
typos.

Reported-by: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/20140115182511.GA22737@gmail.com


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>