x86: Remove unnecessary mdelay() from cpu_disable_common()

fixup_irqs() already has a mdelay(). Remove the extra and
unnecessary mdelay() from cpu_disable_common().

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: ebiederm@xmission.com
Cc: garyhade@us.ibm.com
LKML-Reference: <20091201233335.232177348@sbs-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>