board: gdsys: Drop Dirk Eibach from MAINTAINERS

board: gdsys: Drop Dirk Eibach from MAINTAINERS

I got an

<dirk.eibach@gdsys.cc>: host mxlb.ispgateway.de[80.67.18.126] said:
  554 Sorry, no mailbox here by that name. (in reply to RCPT TO command)

when sending e-mail to dirk.eibach@gdsys.cc.

Drop Dirk Eibach from MAINTAINERS of board/gdsys/a38x and
board/gdsys/mpc8308. The latter would be left maintainerless, add
Mario Six <mario.six@gdsys.cc> (he is also maintainer of the former
board).

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>