MIPS: generic: Add a MAINTAINERS entry

Add an entry to MAINTAINERS for the generic platform code, such that
relevant people, starting with myself, can be CC'd on patches.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16186/


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