MAINTAINERS: Add myself as the co-maintainer for Actions Semi platforms

Since I've been doing the maintainership work for couple of cycles, we've
decided to add myself as the co-maintainer along with Andreas.

Link: https://lore.kernel.org/r/20200114084348.25659-2-manivannan.sadhasivam@linaro.org


Cc: "Andreas Färber" <afaerber@suse.de>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Olof Johansson <olof@lixom.net>