PCI: iproc: Set all 24 bits of PCI class code

Register 0x43c in its low 24 bits contains PCI class code.

Update code to set all 24 bits of PCI class code and not only upper 16 bits
of PCI class code.

Use a new macro PCI_CLASS_BRIDGE_PCI_NORMAL which represents whole 24 bits
of normal PCI bridge class.

Link: https://lore.kernel.org/r/20220214114109.26809-2-pali@kernel.org


Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Roman Bacik <roman.bacik@broadcom.com>
Acked-by: Ray Jui <ray.jui@broadcom.com>