ppc4xx: Add T3COPR board support (PPC460GT based)

This patch adds support for the T3CORP board, based on the
AppliedMicro (APM) PPC460GT.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index d7aec98..9485070 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -392,6 +392,7 @@
 	rainier		PPC440GRx
 	sequoia		PPC440EPx
 	sycamore	PPC405GPr
+	t3corp		PPC460GT
 	taishan		PPC440GX
 	walnut		PPC405GP
 	yellowstone	PPC440GR