imx6: add spl in the header file

add the spl info in the header file.
Also, added a macro statement in m6sabre_common.h to avoid compiler
warning.

Signed-off-by: John Tobias <john.tobias.ph@gmail.com>

include/configs/mx6sabresd.h

@@ -12,6 +12,12 @@
 #include <asm/arch/imx-regs.h>
 #include <asm/imx-common/gpio.h>
 
+#ifdef CONFIG_SPL
+#define CONFIG_SPL_LIBCOMMON_SUPPORT
+#define CONFIG_SPL_MMC_SUPPORT
+#include "imx6_spl.h"
+#endif
+
 #define CONFIG_MACH_TYPE	3980
 #define CONFIG_MXC_UART_BASE	UART1_BASE
 #define CONFIG_CONSOLE_DEV		"ttymxc0"