mips: mtmips: enable SPL for all boards

This patch enables SPL for all mtmips boards. And also remove defconfig
files which are intend to build ram bootable u-boot files.

SPL_DM and OF_CONTROL are enabled for both boards.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
8 files changed