mx6qsabresd: add usdhc2 and usdhc4 support

The on-board number of available usdhc devices is something board
specific.  The patch moves CONFIG_SYS_FSL_USDHC_NUM out of
mx6qsabre_common.h and adds usdhc2 and usdhc4 support for mx6qsabresd
board.

To keep the default mmc device for environment same as before (usdhc3),
it moves CONFIG_SYS_MMC_ENV_DEV out of mx6qsabre_common.h and changes
it to 1 for mx6qsabresd.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

include/configs/mx6qsabre_common.h

@@ -41,7 +41,6 @@
 #define CONFIG_FSL_ESDHC
 #define CONFIG_FSL_USDHC
 #define CONFIG_SYS_FSL_ESDHC_ADDR      0
-#define CONFIG_SYS_FSL_USDHC_NUM       2
 
 #define CONFIG_MMC
 #define CONFIG_CMD_MMC
@@ -166,7 +165,6 @@
 
 #if defined(CONFIG_ENV_IS_IN_MMC)
 #define CONFIG_ENV_OFFSET		(6 * 64 * 1024)
-#define CONFIG_SYS_MMC_ENV_DEV		0
 #endif
 
 #define CONFIG_OF_LIBFDT

include/configs/mx6qsabreauto.h

@@ -20,4 +20,9 @@
 
 #include "mx6qsabre_common.h"
 
+#define CONFIG_SYS_FSL_USDHC_NUM	2
+#if defined(CONFIG_ENV_IS_IN_MMC)
+#define CONFIG_SYS_MMC_ENV_DEV		0
+#endif
+
 #endif                         /* __MX6QSABREAUTO_CONFIG_H */

include/configs/mx6qsabresd.h

@@ -25,4 +25,9 @@
 
 #include "mx6qsabre_common.h"
 
+#define CONFIG_SYS_FSL_USDHC_NUM	3
+#if defined(CONFIG_ENV_IS_IN_MMC)
+#define CONFIG_SYS_MMC_ENV_DEV		1
+#endif
+
 #endif                         /* __MX6QSABRESD_CONFIG_H */