[hammerhead] directfb mode issue

I've got this working on the hammerhead with the info on the debugging wiki page. The current mode I use, which is not the same as fbset -s:

mode "1080x1920-1"
        # D: 1.243 MHz, H: 1.142 kHz, V: 0.593 Hz
        geometry 1080 1920 1080 1920 16
        timings 804667 2 4 2 2 2 2
        accel false
        rgba 5/11,6/5,5/0,0/0
endmode

The hammerhead has still the not-refreshing issue. Apparently this is not really a bug but the way this driver does double buffering, sadly directfb doesn't support this double buffer method yet.

Thanks to zhuowei on IRC we now know that in the android recovery they flip the buffer like this: https://github.com/LineageOS/android_bootable_recovery/blob/6a0693fcce0fea8fd41252ba176aa8e3de33b953/minui/graphics_fbdev.cpp#L77

which is basically the same thing as doing cat mode > mode.

3 possible options for making this work:

1. Add a workaround flag to osk-sdl that does that ioctl on the framebuffer device in the render loop
2. Add this refreshing method to directfb somewhere
3. Write a DRM driver for hammerhead