MLK-22336-2 dts: Add a new usb gadget node on imx6/7/7ulp/8/8mm

MLK-22336-2 dts: Add a new usb gadget node on imx6/7/7ulp/8/8mm

Since one dts node can only bind to one DM driver in uboot, for usbotg
node, we can not use it for both DM usb host driver and DM usb gadget
driver. So a new usb gadget node is added to each usbotg node, the
original usbotg node is bind to usb host driver as default, and the
new usb gadget node is bind to usb gadet driver as default.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 342adc8948def972dbd08b71009584745f7826f0)
(cherry picked from commit 6716cd87079cae70a5c521f83be292628403b9ab)