uboot-phytec

config: enable DFU over USB on Raspberry Pi4 boards

Enable support for DFU over USB. This requires to enable USB gadget,
DWC2 UDC OTG driver and DFU command. DFU entities are defined for the
following firmware objects: u-boot.bin, uboot.env, config.txt, and
zImage/Image.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>