Don't grab memory for LCD if FB address is defined

If FB address is defined specific address then don't grab memory for LCD

Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
Cc: Albert Aribaud <albert.aribaud@free.fr>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Kim Phillips <kim.phillips@freescale.com>
Cc: Andy Fleming <afleming@gmail.com>
Cc: Kumar Gala <kumar.gala@freescale.com>