lcd, fb: remove duplicated prototypes and unused code

cc: Anatolij Gustschin <agust@denx.de>
cc: Cliff Brake <cliff.brake@gmail.com>
cc: John Zhan <zhanz@sinovee.com>
cc: Marek Vasut <marek.vasut@gmail.com>
cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>