alpha: Shift perf event pending work earlier in timer interrupt

Pending work from the performance event subsystem is executed in
the timer interrupt.  This patch shifts the call to
perf_event_do_pending() before the call to update_process_times()
as the latter may call back into the perf event subsystem and it
is prudent to have the pending work executed first.

Signed-off-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Matt Turner <mattst88@gmail.com>