Toggle for optimized auto-address increment for multi-register reads

[Ctru14]

This accel driver currently uses an optimized read pattern for multi-register reads. This allows consecutive registers to be read on only one I2C read command by continuing to clock after the first byte.

However, this mode is only available when the flag CTRL2 IF_ADD_INC is set, and not all the time. Since this control assumption is not guaranteed, the driver should explicitly state that and give an option to not attempt all multi-register reads in one I2C call.