PCI: dwc: pci-dra7xx: Enable errata i870 for both EP and RC mode

Errata i870 is applicable in both EP and RC mode. Therefore rename
function dra7xx_pcie_ep_unaligned_memaccess(), that implements errata
workaround, to dra7xx_pcie_unaligned_memaccess() and call it for both RC
and EP. Make sure driver probe does not fail in case the workaround is not
applied for RC mode in order to maintain DT backward compatibility.

Reported-by: Chris Welch <Chris.Welch@viavisolutions.com>
Signed-off-by: Vignesh R <vigneshr@ti.com>
[lorenzo.pieralisi@arm.com: reworded the log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>