arm/km: rename mgcoge2un to mgcoge3un

The mgcoge2un target was only an intermediate step to mgcoge3un.
For this reason the mgcoge2un support was moved to mgcoge3un,
because it isn't needed to support both targets.

We add the BootROM init file for the mgcoge3un memphis RAM.

We also move the suen3 and suen8 boards into the correct category
in the MAINTAINERS file.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>
cc: Detlev Zundel <dzu@denx.de>
cc: Prafulla Wadaskar <prafulla@marvell.com>
diff --git a/boards.cfg b/boards.cfg
index ced8788..ea5a850 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -108,7 +108,7 @@
 davinci_sonata               arm         arm926ejs   sonata              davinci        davinci
 suen3                        arm         arm926ejs   km_arm              keymile        kirkwood
 suen8                        arm         arm926ejs   km_arm              keymile        kirkwood
-mgcoge2un                    arm         arm926ejs   km_arm              keymile        kirkwood
+mgcoge3un                    arm         arm926ejs   km_arm              keymile        kirkwood
 guruplug                     arm         arm926ejs   -                   Marvell        kirkwood
 mv88f6281gtw_ge              arm         arm926ejs   -                   Marvell        kirkwood
 openrd_base                  arm         arm926ejs   openrd              Marvell        kirkwood        openrd:BOARD_IS_OPENRD_BASE