Moving phosphor-power/tools/i2c into a separated repo

[Lei Yu]

This email is to propose to move the i2c library in phosphor-power to
a separated repo.

In OpenBMC, some repos need i2c/SMBus access to various devices.
E.g.
* phosphor-power implements a C++ wrapper of libi2c in tools/i2c to talk to PSU.
* dbus-sensors is going to have a wrapper to send smbus commands.
* We have an internal (probably will be upstreamed later) repo using
i2c to communicate with a CPLD.

The one in [phosphor-power][1] is a full C++ wrapper, that supports
byte/word/block read/write, supports both I2C and SMBus
communications, and provides a mocked interface for unit tests.
It could be a good candidate for a separate repo so that it could be
shared by other repos.

What do you think?

[1]: https://github.com/openbmc/phosphor-power/tree/master/tools/i2c

-- 
BRs,
Lei YU