microsoft-surface-rt: fix touchscreen detection in osk-sdl, clean up
A workaround for what i mentioned in !2355 (merged).
BTW osk-sdl is really slow. When i type 10 symbols with touchscreen in ~3 seconds i have to wait 15-20 seconds for response. When i do same with TouchCover it is still slow, but in addition some symbols don't appear. Any ideas what can be related? I thought it is because missing GPU acceleration, but osk-sdl works fine with msm8916-based lenovo-a6010, which even does not have GPU firmware in initfs.