Merge serial driver for Quartz64 and Rockpro64

[axel-h]

#117 brings support for the Quartz64 board. It Seems the RK3566 is very similar to the
RK3399 used on the Rockpro64 board, so the the driver code should be unified instead of copy/paste duplicating. As a side effect, this would fix the CR/LF issues from #48 then also.

This is loosely related to RasPi3/RasPi4 driver code unification issue #61 and it would not be a surprise if there are more platforms that run into this. There is the src/mach folder where such driver could end up as an intermediate step. However, mach is considered deprecated as it does not scale too well. Having dedicates driver names makes more sense, so platform can pick what they need. In the end that is how the device tree also works.