arm: socfpga: de0_nano_soc: Consolidate SDMMC environment

Remove the duplication of SDMMC environment configuration
from each boards' configuration header file into
socfpga_common.h

Signed-off-by: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Dinh Nguyen <dinh.linux@gmail.com>
Cc: Pavel Machek <pavel@denx.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Stefan Roese <sr@denx.de>

include/configs/socfpga_de0_nano_soc.h

@@ -48,8 +48,6 @@
 #endif
 
 #define CONFIG_ENV_IS_IN_MMC
-#define CONFIG_SYS_MMC_ENV_DEV		0	/* device 0 */
-#define CONFIG_ENV_OFFSET		512	/* just after the MBR */
 
 /* Extra Environment */
 #define CONFIG_EXTRA_ENV_SETTINGS \