usb: s3c-otg: Rename usb/s3c_udc.h to usb/dwc2_udc.h

The driver is actually for the Designware DWC2 controller.
This patch renames the global s3c_udc.h header to dwc2_udc.h.

The rename is done automatically:
	$ sed -i "s/s3c_udc\.h/dwc2_udc.h/g" \
		`git grep "s3c_udc\.h" | cut -d : -f 1`

Signed-off-by: Marek Vasut <marex@denx.de>