oak: power: set 8s for long power key press to force shutdown
oak: power: set 8s for long power key press to force shutdown

Since the firmware_ECPowerButton testcase holds down power button
about 10s to shut down without powerd, we set DELAY_FORCE_SHUTDOWN
about 8s to make sure the powerbutton is pressed long enough to
force shutdown.

BRANCH=none
BUG=chrome-os-partner:43412
TEST=manual
  run "firmware_ECPowerButton" testcase on rev3.

Change-Id: Ib41cdecfa0342236d618e6fdffcb64bf7f51b557
Signed-off-by: YH Huang <d2b6e71fb6119e288e33a854f7510c1046bfaea5@mediatek.com>
Reviewed-on: https://chromium-review.googlesource.com/296884
Reviewed-by: Rong Chang <3a05493f7adfb36d203f663b3bc2ba30e9d6284f@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,coreboot/chrome-ec