Add system config for servo local ADCS.

Related CL:
http://codereview.chromium.org/6765005/

BUG=chrome-os-partner:2973
TEST=manual

Tried on wario, booted to uboot prompt and idle

chroot>servod -c <path>/servo.xml -c <path>/wario.xml -c <path>/servo_loc.xml
chroot>dut-control i2c_mux_en:on i2c_mux:rem
chroot>dut-control ppvar_vbat_mv ppvar_vbat_mw loc_0x40_mv loc_0x40_shv_reg

Verify that above:
  ppvar_vbat_mw ~= raw_pwr(loc_0x40_mv, loc_0x40_shv_reg, sense_resistor)
See tracker comment #2 for details

Change-Id: I8be25bf531ccd12265ccce8c8a37668e17046eba

Review URL: https://chromereviews.googleplex.com/2668040
6 files changed