Merge and reformat boards.cfg and MAINTAINERS

Put all informations about targets, including state (active or
orphan) and maintainers, in boards.cfg; remove MAINTAINERS;
adjust the build system accordingly.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
diff --git a/README b/README
index 63706be..ccd47fa 100644
--- a/README
+++ b/README
@@ -35,7 +35,7 @@
 "working". In fact, many of them are used in production systems.
 
 In case of problems see the CHANGELOG and CREDITS files to find out
-who contributed the specific port. The MAINTAINERS file lists board
+who contributed the specific port. The boards.cfg file lists board
 maintainers.
 
 Note: There is no CHANGELOG file in the actual U-Boot source tree;
@@ -5833,8 +5833,8 @@
 
 * For major contributions, your entry to the CREDITS file
 
-* When you add support for a new board, don't forget to add this
-  board to the MAINTAINERS file, too.
+* When you add support for a new board, don't forget to add a
+  maintainer e-mail address to the boards.cfg file, too.
 
 * If your patch adds new configuration options, don't forget to
   document these in the README file.