video: fbdev: mmp: remove duplicated MMP_DISP dependency

This dependency is already present in higher level Kconfig file
(drivers/video/fbdev/mmp/Kconfig).

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/eb28587c-4f8f-f044-1b8b-317a8d7967aa@samsung.com