mx6qsabresd: use on-board eMMC to store environment

It makes more sense to use on-board eMMC to store environments.  The
boot partition 1 is selected by default.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

include/configs/mx6qsabresd.h

@@ -27,7 +27,8 @@
 
 #define CONFIG_SYS_FSL_USDHC_NUM	3
 #if defined(CONFIG_ENV_IS_IN_MMC)
-#define CONFIG_SYS_MMC_ENV_DEV		1
+#define CONFIG_SYS_MMC_ENV_DEV		2	/* eMMC/uSDHC4 */
+#define CONFIG_SYS_MMC_ENV_PART		1	/* Boot partition 1 */
 #endif
 
 #endif                         /* __MX6QSABRESD_CONFIG_H */