configs: sama5d2_xplained: set default FAT env location to SD-Card

For sama5d2_xplained_mmc_defconfig, we have the following layout for SD-Card:
partition 1: FAT: contains bootstrap binary (second level bootloader),
U-boot, U-boot env, kernel, dtb
partition 2: EXT4: Rootfs.

Add to defconfig CONFIG_ENV_FAT_DEVICE_AND_PART to have environment
by default on SD-Card, to align with our demo layout.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>

configs/sama5d2_xplained_mmc_defconfig

@@ -40,6 +40,7 @@ CONFIG_OF_CONTROL=y
 CONFIG_SPL_OF_CONTROL=y
 CONFIG_OF_SPL_REMOVE_PROPS="interrupts interrupt-parent dmas dma-names"
 CONFIG_ENV_IS_IN_FAT=y
+CONFIG_ENV_FAT_DEVICE_AND_PART="1:1"
 CONFIG_DM=y
 CONFIG_SPL_DM=y
 CONFIG_SPL_DM_SEQ_ALIAS=y