pico-imx7d: Fix common distro configuration behavior

This sets DISTRO_CONFIG and BOOTCOMMAND, as well as add a `finduuid`
environment helper to allow it to properly work with Yocto Project and
other distributions using extlinux autogenerated configuration files.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
diff --git a/configs/pico-imx7d_defconfig b/configs/pico-imx7d_defconfig
index ef52dcb..7be695c 100644
--- a/configs/pico-imx7d_defconfig
+++ b/configs/pico-imx7d_defconfig
@@ -3,26 +3,23 @@
 CONFIG_SYS_TEXT_BASE=0x87800000
 CONFIG_TARGET_PICO_IMX7D=y
 CONFIG_IMX_RDC=y
+CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/technexion/pico-imx7d/imximage.cfg"
-CONFIG_HUSH_PARSER=y
+CONFIG_BOOTCOMMAND="run finduuid; run distro_bootcmd"
 # CONFIG_CMD_BOOTD is not set
-CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_XIMG is not set
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y
-CONFIG_CMD_PART=y
 CONFIG_CMD_USB=y
 CONFIG_CMD_USB_MASS_STORAGE=y
 # CONFIG_CMD_SETEXPR is not set
-CONFIG_CMD_DHCP=y
+# CONFIG_CMD_MII is not set
 CONFIG_CMD_CACHE=y
-CONFIG_CMD_EXT2=y
-CONFIG_CMD_EXT4=y
 CONFIG_CMD_EXT4_WRITE=y
-CONFIG_CMD_FAT=y
-CONFIG_CMD_FS_GENERIC=y
+# CONFIG_ISO_PARTITION is not set
+# CONFIG_EFI_PARTITION is not set
 CONFIG_FSL_ESDHC=y
 CONFIG_PHYLIB=y
 CONFIG_USB=y