arm: adds the status info for odroid-xu3

Adds the 'F:' entry for the board's defconfig

Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/board/samsung/smdk5420/MAINTAINERS b/board/samsung/smdk5420/MAINTAINERS
index a26ea68..0361657 100644
--- a/board/samsung/smdk5420/MAINTAINERS
+++ b/board/samsung/smdk5420/MAINTAINERS
@@ -14,3 +14,4 @@
 S:	Maintained
 F:	board/samsung/smdk5420/
 F:	include/configs/odroid_xu3.h
+F:	configs/odroid-xu3_defconfig