README: Any sdcc 3.x version works fine.
README: Any sdcc 3.x version works fine.

E.g. 3.5 also works fine as of today.

uffejakobsen/sigrok-firmware-fx2lafw,uffejakobsen/sigrok-firmware-fx2lafw,swegener/sigrok-firmware-fx2lafw,swegener/sigrok-firmware-fx2lafw,swegener/sigrok-firmware-fx2lafw,swegener/sigrok-firmware-fx2lafw,uffejakobsen/sigrok-firmware-fx2lafw,uffejakobsen/sigrok-firmware-fx2lafw