[PATCH RTEMS] Add i2c command

[chrisj at rtems.org]

The patch adds the i2c command. It is a single command to test and 
explore I2C buses on hardware. The command lets you string together
reads and writes on a single command line to access a number of devices
so you can script basic functionality simply.

This ocommand adds to the existing i2cdetect, i2cset and i2cget however
those commands did not work cleanly on the vck-190 or did not read and
write directly at the bus level.

Chris