Add missing rainier (PPC440GRx) target to MAKEALL and MAINTAINERs files

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index f812431..bb329ad 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -296,6 +296,7 @@
 	ocotea			PPC440GX
 	p3p440			PPC440GP
 	pcs440ep		PPC440EP
+	rainier			PPC440GRx
 	sequoia			PPC440EPx
 	sycamore		PPC405GPr
 	taishan			PPC440GX