platform/x86: i2c-multi-instantiate: Allow to have same slaves

Currently the driver will not enumerate the devices where I2C slaves
are of the same type.

Add an instance number to make them unique.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>