drivers: usb: udc: prevent USB clock disable in sleep mode

Prevent disabling OTG HS and USBPHY clocks
during sleep on STM32U5 series

Disabling these clocks during sleep mode
was causing USB device initialization issues

Signed-off-by: IBEN EL HADJ MESSAOUD Marwa <marwa.ibenelhadjmessaoud-ext@st.com>