ARM: mmp: remove the legacy rbswap setting for ttc_dkb platform

According to new rbswap scheme of mmp_display, it support appropriate
rbswap setting based on specific pix_fmt, then we can remove the legacy
rbswap setting for ttc_dkb platform.

Signed-off-by: Jett.Zhou <jtzhou@marvell.com>
Signed-off-by: Zhou Zhu <zzhu3@marvell.com>
Reviewed-by: Daniel Drake <dsd@laptop.org>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>