There's nothing ACPI-specific about the config space accessors
hisi_pcie_acpi_rd_conf() and hisi_pcie_acpi_wr_conf(), and they're used for
both the ACPI and the DT driver model.

Rename them to hisi_pcie_rd_conf() and hisi_pcie_wr_conf().  No functional
change intended.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>