Added special UART4 init to sample if FlySky sticks are present or not.
Added boolean globalData.flyskygimbals to save the detection result.
Removed FLYSKY_HALL_STICKS and FLYSKY_HALL_STICKS_REVERSE CMake build options.
Tested on two RM TX16S radios, one with FlySky digital hall sticks and second with stock analog sticks.
Before write access is permitted to numerous DMA registers, need to make sure that DMA is disabled for the stream. Disabling the stream is not instantaneous, and needs to be waited for (previous transmissions need to be finished first).
Added return values to numerous functions to signal a failure.