stepper motor controller: introduce api

This commit introduces api for stepper motor controllers

Signed-off-by: Dipak Shetty <dipak.shetty@zeiss.com>
Signed-off-by: Florian Guhl <florian.guhl@zeiss.com>
Signed-off-by: Jilay Pandya <jilay.pandya@zeiss.com>
Signed-off-by: Fabian Blatz <fabianblatz@gmail.com>