[FluidNC PR#1589] Fix issue with SH1106 OLED Display

I had issue with a screen controlled by SH1106 controller.
It’s a common 128*64 OLED display often sold as “SSD1306”; it’s mostly compatible but 1106 is more dumb.

The screen is initialized, the charge pump works (there is a visible image on the screen).
There is a small horizontal rectangular window, around 10 pixels high, displaying part of the image. However, the majority of the screen is filled with garbage, mostly white with some black dots on it.

After some fiddling around with U8g2 library, I understood the actual controller name.
As far as I see, those are mostly interchangeable; since FluidNC does not use any advanced features of 1306 (scrolling and offseting), I feel the fix might be useful for some users.