Revert "overlays: Add Pi 5 version of dwc2"

This reverts commit ff2db584

.

We don't need a special dwc2 overlay for Pi 5, with a node to limit the
DMA zone to the first 1GB, since it turns out that the USB2 controller
has a 4GB range after all.

See https://github.com/raspberrypi/linux/pull/5772

Signed-off-by: Phil Elwell <phil@raspberrypi.com>