i2c: Add request/release_mem_region to i2c-ibm_iic bus driver

Reserving I/O memory for a driver with request_mem_region is necessary to
avoid memory access conflicts. Even if it's never going to happen, it is
cleaner and it allows to monitor I/O memory used in /proc/iomem.

Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@teamlog.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>