ARM: dts: stm32: Add USB OTG pinctrl and regulator nodes into SPL DT on DHCOR

Fix the following warning in SPL and make sure that even DTs which
enforce Vbus detection using u-boot,force-vbus-detection;, the DFU
in SPL will work.

dwc2-udc-otg usb-otg@49000000: prop pinctrl-0 index 0 invalid phandle

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>