flash_ec: enable i2c_mux before it uses I2C interface
flash_ec: enable i2c_mux before it uses I2C interface

This is for it83xx EC.
i2c_mux should be enabled before it does
	dut-control jtag_buf_on_flex_en
, which uses i2c interface.

Also during cleanup, servo setting should be restored
after ftdii2c initialization and i2c_mux enabling.

BUG=b:127696997
BRANCH=none
TEST=ran flash_ec on Ampel with servo_v2 or Suzy-Q

- servo_v2: http://gpaste/4877399499997184
- Suzy-Q:   http://gpaste/5150426007601152

Tested with a fake board name for servod,
and flash_ec without --board and --chip.

$ ./util/flash_ec --image /tmp/a  --verbose
ERROR: Please check that servod is running or \
manually specify either --board or --chip.

Tested without launching servod:
 ./util/flash_ec --board=coral --image /tmp/a  --verbose
Connection refused
dut-control --port=9999 servo_type
Connection refused
ERROR: board 'coral' not supported. Please check \
that servod is running, or manually specify --chip.

Change-Id: I8106c2f08fd74c8d86c985562cd4e1771df65287
Signed-off-by: Namyoon Woo <e8732cefb861f07768f47df788a8e8eb75efc09a@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1506446
Reviewed-by: Matthew Blecker <d18f4466f2802f9c78c5c14a42b8c21fdbfabfcd@chromium.org>

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