PCI: layerscape: Move STRFMR1 access out from the DBI write-enable bracket

The STRFMR1 is not a DBI read-only register, so move it out from the
write-enable bracket.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Roy Zang <tie-fei.zang@freescale.com>