uboot-imx

usb: dfu: add fullspeed support for DFU

DFU now can use also fullspeed.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Liu Bin <b-liu@ti.com>
Cc: Lukas Stockmann <lukas.stockmann@siemens.com>