mips: ci20_defconfig: Add clock_ignore_unused to ci20 defconfig

without clock_ignore_unused, the kernel hangs during boot.

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
dt: ci20: use bootargs from u-boot instead of dt

Currently the linux kernel uses bootargs from dt instead of taking
them from u-boot.

This patch changes that to take the bootargs from u-boot instead.

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>