evb-rk3399: config: set emmc as default boot dev

rk3399 has two mmc dev controller:
mmc 0: SD card;
mmc 1: EMMC

U-Boot will scan the mmc boot device configured by CONFIG_SYS_MMC_ENV_DEV,
since evb has emmc on board, let's set the EMMC as default.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>

include/configs/evb_rk3399.h

@@ -10,7 +10,7 @@
 #include <configs/rk3399_common.h>
 
 #define CONFIG_ENV_IS_IN_MMC
-#define CONFIG_SYS_MMC_ENV_DEV 0
+#define CONFIG_SYS_MMC_ENV_DEV 1
 /*
  * SPL @ 32k for ~36k
  * ENV @ 96k