cypress-fx2/Makefile: Add missing 'fx2lafw-' prefix.
cypress-fx2/Makefile: Add missing 'fx2lafw-' prefix.

Otherwise the generated .fw filename will be incorrect.

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