Remove USB support for tl-mr3020

USB support is removed because of very limited flash.
This allows building for tl-mr3020 again.

USB support has no known use case for this firmware.
Most usb devices would require additional drivers anyway.

Signed-off-by: Fabian Bläse <fabian@blaese.de>
Reviewed-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

bsp/ar71xx/.config

@@ -15,7 +15,7 @@ CONFIG_TARGET_DEVICE_PACKAGES_ar71xx_tiny_DEVICE_cpe210-220-v1=""
 CONFIG_TARGET_DEVICE_ar71xx_tiny_DEVICE_cpe510-520-v1=y
 CONFIG_TARGET_DEVICE_PACKAGES_ar71xx_tiny_DEVICE_cpe510-520-v1=""
 CONFIG_TARGET_DEVICE_ar71xx_tiny_DEVICE_tl-mr3020-v1=y
-CONFIG_TARGET_DEVICE_PACKAGES_ar71xx_tiny_DEVICE_tl-mr3020-v1="-uboot-envtools"
+CONFIG_TARGET_DEVICE_PACKAGES_ar71xx_tiny_DEVICE_tl-mr3020-v1="-uboot-envtools -kmod-usb-core -kmod-usb2 -kmod-usb-ledtrig-usbport"
 CONFIG_TARGET_DEVICE_ar71xx_tiny_DEVICE_tl-wa850re-v1=y
 CONFIG_TARGET_DEVICE_PACKAGES_ar71xx_tiny_DEVICE_tl-wa850re-v1=""
 CONFIG_TARGET_DEVICE_ar71xx_tiny_DEVICE_tl-wa860re-v1=y