PCI: dwc: Add validation that PCIe core is set to correct mode

Some PCIe controllers can be set to either Host or EP according to some
early boot FW. To make sure there is no discrepancy (e.g. FW configured
the port to EP mode while the DT specifies it as a host bridge or vice
versa), a check has been added for each mode.

Signed-off-by: Jonathan Chocron <jonnyc@amazon.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>