driver: i2c: npcx_controller: use the non I2C device init macro

The i2c_npcx_controller does not actually implement the i2c API, that's
implemented in the port driver and the controller one is in support of
that. This means there's no need to use the I2C specific instance
define, as that would end up adding the stats structure that would never
get used.

This was originally added in 7b1349cf.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>