test/py: i2c: Add tests for i2c command

Add below test cases for i2c commands:
i2c_bus - To show i2c bus info,
i2c_dev - To set or show the current bus,
i2c_probe - To probe the i2c device,
i2c_eeprom - To test i2c eeprom device,
i2c_probe_all_buses - To list down all the buses and probes it

Signed-off-by: Love Kumar <love.kumar@amd.com>
Reviewed-by: Tom Rini <trini@konsulko.com>