PCI: mvebu: Remove unused busn member

The busn member of struct mvebu_pcie is unused, so drop it.

Link: https://lore.kernel.org/r/20220905192310.22786-5-pali@kernel.org


Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>