MAINTAINERS: add myself as Methode maintainer

I am currently maintaing the Methode uDPU and eDPU boards so add myself
as the maintainer for them.

Remove the old entry from board/Marvell/mvebu_armada-37xx/MAINTAINERS.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>