apalis-imx8: remove obsolete net usb start

Remove obsolete net USB start.

While at it also add a comment about enabling distro-boot.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/include/configs/apalis-imx8.h b/include/configs/apalis-imx8.h
index 6b0541f..5d1ee49 100644
--- a/include/configs/apalis-imx8.h
+++ b/include/configs/apalis-imx8.h
@@ -17,14 +17,13 @@
 	"ramdisk_addr_r=0x94400000\0" \
 	"scriptaddr=0x87000000\0"
 
+/* Enable Distro Boot */
 #define BOOT_TARGET_DEVICES(func) \
 	func(MMC, mmc, 1) \
 	func(MMC, mmc, 2) \
 	func(MMC, mmc, 0) \
 	func(DHCP, dhcp, na)
 #include <config_distro_bootcmd.h>
-#undef BOOTENV_RUN_NET_USB_START
-#define BOOTENV_RUN_NET_USB_START ""
 
 /* Initial environment variables */
 #define CFG_EXTRA_ENV_SETTINGS \