dts/arm: stm32u5: add usb OTG full-speed node

Add the USB On-The-Go Supplement, Revision 2.0 in the DTS
of the stm32u575 and stm32u585 devices
(not for the stm32U5 serie).

Signed-off-by: Francois Ramu <francois.ramu@st.com>