x86/time: do not kill calibration timer on suspend

A killed timer will ignore further set_timer() calls, and hence won't be
re-armed unless it's initialized again.  Use stop_timer() instead of
kill_timer() in time_suspend(), so that the set_timer() call in
time_resume() successfully re-arms the timer.  Otherwise time calibration
is no longer scheduled (and executed) after resuming from S3 suspend.

Fixes: 6d90db1a2c ("x86: rendezvous-based local time calibration")
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

xen/arch/x86/time.c

@@ -2728,7 +2728,7 @@ int time_suspend(void)
     {
         cmos_utc_offset = -get_wallclock_time();
         cmos_utc_offset += get_sec();
-        kill_timer(&calibration_timer);
+        stop_timer(&calibration_timer);
 
         /* Sync platform timer stamps. */
         platform_time_calibration();