[hdctools] servod: add PCA9546 driver support.

BUG=chrome-os-partner:6511
TEST=manual,

- launch servod
sudo servod -c servo.xml -c waluigi.xml -c servo_loc.xml

- setup
dut-control i2c_mux_en:on i2c_mux:rem

- read bank0
dut-control waluigi_adc_mux:bank0
dut-control loc_0x40_mv loc_0x41_mv loc_0x42_mv loc_0x43_mv loc_0x44_mv loc_0x45_mv loc_0x46_mv loc_0x47_mv loc_0x48_mv loc_0x49_mv loc_0x4a_mv loc_0x4b_mv loc_0x4c_mv loc_0x4d_mv loc_0x4e_mv loc_0x4f_mv

- read bank1
dut-control waluigi_adc_mux:bank1
dut-control loc_0x40_mv loc_0x41_mv loc_0x42_mv loc_0x43_mv loc_0x44_mv loc_0x45_mv loc_0x46_mv loc_0x47_mv loc_0x48_mv loc_0x49_mv loc_0x4a_mv loc_0x4b_mv loc_0x4c_mv loc_0x4d_mv loc_0x4e_mv loc_0x4f_mv

Change-Id: If20539b284cfb54e8dfb28382b7ca205b655369c
Reviewed-on: https://gerrit.chromium.org/gerrit/10408
Commit-Ready: Todd Broch <tbroch@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
4 files changed