npcx: watchdog: disable ITIM16 before updating ITCNT register
npcx: watchdog: disable ITIM16 before updating ITCNT register

During watchdog initialization, the driver doesn't disable ITIM16
module which used for detecting watchdog timeout before updating
new preload value. Although the ITEN bit on reset is zero, it caused
preload value is not updated to module successfully since ITEN won't
be reset (ITIM16 is still enabled) in sysjump case.

Despite WDCNT will be reloaded by touching watchdog in HOOK_TICK
hook function later, it's better to disable any ITIM16 module before
updating ITCNT register.

BRANCH=none
BUG=b:77336821
TEST=No build errors for npcx5 series.

Change-Id: I19baa47bca347b9dca2fc1dcaacca81519facf21
Signed-off-by: Mulin Chao <6bbc5af053a1dfdc363be6857f30de4ac3bcbd16@nuvoton.com>
Reviewed-on: https://chromium-review.googlesource.com/999458
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec