You can also create an invisible quad as a ramp just above your stairs and give that quad collisions (response-type 3 prevents your character to slide down this ramp when not moving).
Then your character will use this ramp to "slide" it's way to the top of the stairs, just moving your character forwards will do the trick.
Then your character will use this ramp to "slide" it's way to the top of the stairs, just moving your character forwards will do the trick.