Staging: most: add MOST driver's hdm-i2c module

This patch adds the hdm-i2c module of the MOST driver to the kernel's
driver staging area. This module is part of the MOST driver and handles
the I2C interface of the MOST network interface controller.

This patch is needed in order to use the I2C peripheral interface of the
network interface controller.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>