MIPS: APRP: Split RTLX support into separate files.

Split the RTLX functionality in preparation for adding support for CMP
platforms. Common functions remain in the original file and a new file
contains code specific to platforms that do not have a CMP.

Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@imgtec.com>
Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Reviewed-by: Qais Yousef <Qais.Yousef@imgtec.com>
Patchwork: http://patchwork.linux-mips.org/patch/6093/


Reviewed-by: John Crispin <blogic@openwrt.org>