x86/mrst: Fix apb timer rating when lapic timer is used

Need to adjust the clockevent device rating for the structure
that will be registered with clockevent system instead of the
temporary structure.

Without this fix, APB timer rating will be higher than LAPIC
timer such that it can not be released later to be used as the
broadcast timer.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
LKML-Reference: <1298506046-439-1-git-send-email-jacob.jun.pan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>