powerpc/defconfig: Rename defconfig file for T1040QDS/T1024QDS DDR4 targets

Previously the DDR4 targets were named with _D4. Rename them with
_DDR4 for easy identification.

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/board/freescale/t1040qds/MAINTAINERS b/board/freescale/t1040qds/MAINTAINERS
index 83f6b3c..640538f 100644
--- a/board/freescale/t1040qds/MAINTAINERS
+++ b/board/freescale/t1040qds/MAINTAINERS
@@ -4,7 +4,7 @@
 F:	board/freescale/t1040qds/
 F:	include/configs/T1040QDS.h
 F:	configs/T1040QDS_defconfig
-F:	configs/T1040QDS_D4_defconfig
+F:	configs/T1040QDS_DDR4_defconfig
 
 T1040QDS_SECURE_BOOT BOARD
 M:	Aneesh Bansal <aneesh.bansal@freescale.com>