Update scramble to specially handle >8-bit banks

[evie-calico]

I realized that scramble could be made more useful for 9-bit banks if it alternated between setting the 9th bit; now both bytes are scrambled.

[ISSOtm]

RGBLINK supports 32-bit section IDs, so a special-case for 512 banks is not viable. Trying to change every byte on each iteration would be closer, but doesn't play nice with non-powers of two as the argument.