PCI: endpoint: Setting BAR_5 to 64-bits wide is invalid

Since a 64-bit BAR consists of a BAR pair, and since there is no
BAR after BAR_5, BAR_5 cannot be 64-bits wide.

This sanity check is done in pci_epc_set_bar(), so that we don't need
to do this sanity check in all epc->ops->set_bar() implementations.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>