DISPLAY_SWAP_BGR was not swapping colours, according to pg 192 of (In…

[alxhoff]

…terface Control), MADCTL is set to XOR of IFCTL and MADCTL, setting 0 to IFCTL before MADCTL is set to ensure passed MADCTL byte is set.

Was having issues with BGR colours on my Pi Zero and generic ILI9341, I believe this is the root of the issue. Fixed it for me.

[juj]

Thanks for the contribution. It is odd that toggling MADCTL_BGR_PIXEL_ORDER did not invert BGR, because like the spec says, it is treated as an XOR of the bit value. Then passing either 0 or 1 should cause a flipped value.

If this PR works, it seems as if the result is more like a NAND ratherthan XOR, i.e. a ~IFCTL & MADCTL instead of IFCTL ^ MADCTL?

Without this PR, did both enabled and disabled cases of DISPLAY_SWAP_BGR produce the same wrong colors?

[alxhoff]

I will have it another test over the weekend. My guess was that IFCTL was not always zero'd out when setting MADCTL.