The PCIE_DBI_RO_WR_EN bit should be set when write some DBI registers.  To
make sure that the DBI registers are writable, set the PCIE_DBI_RO_WR_EN
properly when writing the DBI registers.

Link: https://lore.kernel.org/r/1652866528-13220-1-git-send-email-hongxing.zhu@nxp.comSigned-off-by: NRichard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>