Ampere eMAG systems have XHCI just descibed in ACPI, not on PCI.
We don't actually need xhcireg (I think I've seen an error related to that earlier, but removing it is fine now). We need xhci for the softc and all other USB stuff for xhci…
Tinh Nguyen from Ampere tested and it doesn't seems to make usb working (xhci controller is discovered but nothing more), I've tried on my overdrive in FDT mode and it works.
In acpi mode this doesn't but it doesn't without this patch too, looks like the acpi table is missing info about interrupts, I'll do one more test on the macchiatobin and then commit this.