odroid: Fix target platform compilation issue on Odroid-XU3

Resolved a compilation issue where the build system attempted
to compile for the Odroid-XU3 platform instead of the specified
Exynos4412 platform due to an incorrect CONFIG_SYS_BOARD setting.
Updated the Makefile to ensure that compilation only occurs for
the Odroid-XU3 specified target platform.

Now, object files will be generated only when building for the
TARGET_ODROID platform.

Signed-off-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/board/samsung/odroid/Makefile b/board/samsung/odroid/Makefile
index 5bf4831..615c99f 100644
--- a/board/samsung/odroid/Makefile
+++ b/board/samsung/odroid/Makefile
@@ -3,4 +3,4 @@
 # Copyright (c) 2014 Samsung Electronics Co., Ltd. All rights reserved.
 # Przemyslaw Marczak <p.marczak@samsung.com>
 
-obj-y	:= odroid.o
+obj-$(CONFIG_TARGET_ODROID)	:= odroid.o