flash_ec: iteflash: modify process

With this change, we can do flashing via flex cable.

BRANCH=none
BUG=b:35573714
TEST=To run "~/trunk/src/platform/ec/util/flash_ec --board=reef_it8320"
     and flashing is done and cold reset automatically.

CQ-DEPEND=CL:855978

Change-Id: I078afa6d6f6f8f7bf60a1677e4c357dbe906e7dc
Signed-off-by: Donald Huang <donald.huang@ite.com.tw>
Signed-off-by: Dino Li <Dino.Li@ite.com.tw>
Reviewed-on: https://chromium-review.googlesource.com/344481
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

util/flash_ec

@@ -819,7 +819,20 @@ function flash_it83xx() {
 	if [ ! -x "$ITEFLASH" ]; then
 		die "no iteflash util found."
 	fi
+
+	dut_control i2c_mux_en:on
+	dut_control i2c_mux:remote_adc
+
+	info "Close connection to ftdi_i2c interface"
+	dut_control --ftdii2c close
+
+	info "Run iteflash..."
 	sudo ${ITEFLASH} -w ${IMG}
+
+	info "Reinitialize ftdi_i2c interface"
+	dut_control --ftdii2c init
+	dut_control --ftdii2c open
+	dut_control --ftdii2c setclock
 }
 
 function flash_lm4() {