it83xx: i2c: fix i2c stop bit
it83xx: i2c: fix i2c stop bit

We disable i2c interface immediately after stop bit is set.

This might caused bus busy bit of status register unable to clear
(bus busy bit will be set at start condition and cleared at
stop condition).
So the next transaction, we won't get a good state to start.

This change also fix incorrect stop bit for write transaction:
IT83XX_I2C_CTR(p_ch) = xx

BRANCH=none
BUG=none
TEST=Ensure i2c interface is disabled after i2c stop condition.

Change-Id: I5416bfcef3f95357c6771dead6b0611b908f787e
Signed-off-by: Dino Li <338d523ecf3700bd86eb9c34d220f91911d2a18c@ite.com.tw>
Reviewed-on: https://chromium-review.googlesource.com/645407
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