close race condition window in expired timer processing
close race condition window in expired timer processing

ensure we cannot miss any timer, no matter how slow is the CPU and how
many simultaneous timer we set.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BUG=chrome-os-partner:9319
TEST=boot Link EC and do long key press, see the EC watchdog panic no
longer happening.

Change-Id: I1ecc88fc06698175444fd86cce4c0abb5e846996

coreboot/chrome-ec,longsleep/ec,coreboot/chrome-ec,thehobn/ec,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,md5555/ec,alterapraxisptyltd/chromium-ec,gelraen/cros-ec,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,alterapraxisptyltd/chromium-ec,fourier49/BIZ_EC,mtk09422/chromiumos-platform-ec,thehobn/ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,md5555/ec,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,coreboot/chrome-ec,coreboot/chrome-ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,thehobn/ec,coreboot/chrome-ec,longsleep/ec,longsleep/ec,mtk09422/chromiumos-platform-ec,md5555/ec,thehobn/ec,gelraen/cros-ec,mtk09422/chromiumos-platform-ec,gelraen/cros-ec,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,gelraen/cros-ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,longsleep/ec