uboot-imx

arm: am335x: siemens board use in DFU mode fullspeed only

Siemens boards are now using DFU in fullspeed only. For
this CONFIG_USB_GADGET_DUALSPEED is undefined.

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>