ARM: rpi_*_defconfig: Add support to find UUID for filesystem

The most generic way of having a stable boot behavior is to rely on
UUID instead of device names for root partition, so the order of
probing does not cause issues with booting.

This enables the `CMD_FS_UUID` for following defconfig files:

 - rpi_0_w_defconfig
 - rpi_2_defconfig
 - rpi_3_32b_defconfig
 - rpi_3_defconfig
 - rpi_defconfig

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Fabio Berton <fabio.berton@ossystems.com.br>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/configs/rpi_2_defconfig b/configs/rpi_2_defconfig
index a50a815..ba75e52 100644
--- a/configs/rpi_2_defconfig
+++ b/configs/rpi_2_defconfig
@@ -13,6 +13,7 @@
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_USB=y
+CONFIG_CMD_FS_UUID=y
 CONFIG_OF_EMBED=y
 CONFIG_DEFAULT_DEVICE_TREE="bcm2836-rpi-2-b"
 CONFIG_ENV_FAT_INTERFACE="mmc"