Add dwc_otg_acpi

Create an acpi attachment for the DWC USB OTG device. This is present in
the Raspberry Pi 4 in the USB-C port normally used to power the board. Some
firmware presents the kernel with ACPI tables rather than FDT so we need
an ACPI attachment.

Submitted by: Greg V <greg_unrelenting.technology>
Approved by: hselasky (removal of All rights reserved)
Differential Revision: https://reviews.freebsd.org/D25203