MIPS: XPA: Add new configuration file.

Add in new config files for enabling a XPA platform.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9354/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>