qemu: Remove use of piix3-uhci for non-x86

qemu: Remove use of piix3-uhci for non-x86

There are still a couple of scenarios in which we end up
using the Intel-specific piix3-uhci (USB1) controller for
non-x86 guests.

Remove these uses, leaving the generic pci-ohci (USB1)
controller as either the fallback or default for situations
where no better choice can be made.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>