x86, apbt: Setup affinity for apb timers acting as per-cpu timer

Commit a5ef2e70 "x86: Sanitize apb timer interrupt handling" forgot
the affinity setup when cleaning up the code, this patch just
adds the forgotten part

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Jacob Pan <jacob.jun.pan@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
LKML-Reference: <1291348298-21263-2-git-send-email-feng.tang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>