ti: am335x: mmc: Set CONFIG_SYS_MMC_MAX_DEVICE

Set CONFIG_SYS_MMC_MAX_DEVICE to 2 for am335x SoC.
This define is needed in the API code.

Signed-off-by: Emmanuel Vadot <manu@bidouilliste.com>

include/configs/am335x_evm.h

@@ -347,6 +347,7 @@
 #define CONFIG_ENV_OFFSET		0x0
 #define CONFIG_ENV_OFFSET_REDUND	(CONFIG_ENV_OFFSET + CONFIG_ENV_SIZE)
 #define CONFIG_SYS_REDUNDAND_ENVIRONMENT
+#define CONFIG_SYS_MMC_MAX_DEVICE	2
 #elif defined(CONFIG_NOR_BOOT)
 #define CONFIG_ENV_IS_IN_FLASH
 #define CONFIG_ENV_SECT_SIZE		(128 << 10)	/* 128 KiB */