PCI: endpoint: Handle 64-bit BARs properly

If a 64-bit BAR was set-up, we need to skip a BAR,
since a 64-bit BAR consists of a BAR pair.

We need to check what BAR width the epc->ops->set_bar() specific
implementation actually did set-up, since some drivers, like the
Cadence EP controller, sometimes sets up a 64-bit BAR, even though
a 32-bit BAR was requested.

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>