i2c-tools: add support to build python extension

Add a config option to build the python bindings for i2c-tools -
py-smbus. The steps for building the python bindings is the same as
the distutil steps that are a part of the python infrastructure.

Signed-off-by: Ryan Barnett <ryanbarnett3@gmail.com>
CC: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
CC: Baruch Siach <baruch@tkos.co.il>
CC: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>