it83xx/i2c: adjust Tlow and Thigh of 400kHz clock
it83xx/i2c: adjust Tlow and Thigh of 400kHz clock

This CL increased clock's Tlow to 1.51 us (1.3 us minimum) and
reduced Thigh to 1.087 us (0.6 us minimum).

BUG=b:163384683
BRANCH=none
TEST=i2c clock meet timing at 400kHz.

Signed-off-by: Dino Li <338d523ecf3700bd86eb9c34d220f91911d2a18c@ite.com.tw>
Change-Id: Id62b2370018ba2d41e0dbc715a4c40629260d66b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2557281
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Reviewed-by: Mike Goodey <d8f4c0a56f0726f1427e4274c0cf4552294f3bd0@google.com>
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>

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