MIPS: Lantiq: Add platform device support

This patch adds the wrappers for registering our platform devices.

Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: Ralph Hempel <ralph.hempel@lantiq.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2254/
Patchwork: https://patchwork.linux-mips.org/patch/2360/
Patchwork: https://patchwork.linux-mips.org/patch/2359/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>