PCI: ECAM: Map config region with pci_remap_cfgspace()

PCI: ECAM: Map config region with pci_remap_cfgspace()

The current ECAM kernel implementation uses ioremap() to map the ECAM
configuration space memory region; this is not safe in that on some
architectures the ioremap interface provides mappings that allow posted
write transactions. This, as highlighted in the PCIe specifications (4.0 -
Rev0.3, "Ordering Considerations for the Enhanced Configuration Address
Mechanism"), can create ordering issues for software because posted writes
transactions on the CPU host bus are non posted in the PCI express fabric.

Update the ioremap() interface to use pci_remap_cfgspace() whose mapping
attributes guarantee that non-posted writes transactions are issued for
memory writes within the ECAM memory mapped address region.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jayachandran C <jnair@caviumnetworks.com>