hw/pci: Assert a bar is not registered multiple times

hw/pci: Assert a bar is not registered multiple times

Nothing should be doing this, but it doesn't get caught by
pci_register_bar(). Add an assertion to prevent misuse.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20250117172842.406338-3-npiggin@gmail.com>
Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>