treewide: Fix gdsys mail addresses

The @gdsys.cc addresses are supposed to be used for mailing lists.
Switch all occurrences of @gdsys.de mail addresses to their @gdsys.cc
equivalent.

Also, Dirk's address was wrong in one place; fix that as well.

Signed-off-by: Mario Six <six@gdsys.cc>
diff --git a/board/gdsys/common/ioep-fpga.c b/board/gdsys/common/ioep-fpga.c
index f72a01e..7ebce04 100644
--- a/board/gdsys/common/ioep-fpga.c
+++ b/board/gdsys/common/ioep-fpga.c
@@ -1,6 +1,6 @@
 /*
  * (C) Copyright 2014
- * Dirk Eibach,  Guntermann & Drunck GmbH, eibach@gdsys.de
+ * Dirk Eibach,  Guntermann & Drunck GmbH, dirk.eibach@gdsys.cc
  *
  * SPDX-License-Identifier:	GPL-2.0+
  */