Refactor board/chip-specific code into corresponding directories.
Add support of the four I2C temp sensor in Link.
Use table lookup to handle different types of temperature sensors.
BUG=chrome-os-partner:7527
TEST=Correctly read EC internal temperature on bds.
Compile for link succeeded.
Change-Id: I694cfa54e1545798d877fafdf18c5585ab5f03e2