exynos5: Enable generic board for Exynos5 device tree boards

Enable CONFIG_SYS_GENERIC_BOARD for all Exynos5 boards that use
CONFIG_OF_CONTROL.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/configs/exynos5250-dt.h

@@ -33,6 +33,7 @@
 
 #include <asm/arch/cpu.h>		/* get chip and board defs */
 
+#define CONFIG_SYS_GENERIC_BOARD
 #define CONFIG_ARCH_CPU_INIT
 #define CONFIG_DISPLAY_CPUINFO
 #define CONFIG_DISPLAY_BOARDINFO