mx6_common: Do not select esdhc DDR mode for all boards

CONFIG_SYS_FSL_ESDHC_HAS_DDR_MODE should be selected only by boards that really
have a DDR-capable eMMC, so remove this option from common code to avoid
regressions.

Reported-by: Stefan Roese <sr@denx.de>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>
Reviewed-by: Volodymyr Riazantsev <volodymyr.riazantsev@globallogic.com>
Tested-by: Stefan Roese <sr@denx.de>

include/configs/mx6_common.h

@@ -28,8 +28,6 @@
 #define CONFIG_SYS_PL310_BASE	L2_PL310_BASE
 #endif
 
-#define CONFIG_SYS_FSL_ESDHC_HAS_DDR_MODE
-
 #define CONFIG_MP
 #define CONFIG_MXC_GPT_HCLK