usb: host: dwc2: add trace to have clean usb start

Solve issue for the display of "usb start" command on stm32mp1
because one carriage return is missing in DWC2 probe.

Before the patch:

STM32MP> usb start
starting USB...
Bus usb-otg@49000000:    Bus usbh-ehci@5800d000:   USB EHCI 1.00

after the patch:

STM32MP> usb start
starting USB...
Bus usb-otg@49000000: USB DWC2
Bus usbh-ehci@5800d000: USB EHCI 1.00

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>