PCI: imx6: Limit DBI register length for imx6qp PCIe

Define the length of the DBI registers and limit config space to its
length. This makes sure that the kernel does not access registers beyond
that point that otherwise would lead to an abort on the i.MX 6QuadPlus.

See commit 075af61c ("PCI: imx6: Limit DBI register length") that
resolves a similar issue on the i.MX 6Quad PCIe.

Link: https://lore.kernel.org/r/1613789388-2495-2-git-send-email-hongxing.zhu@nxp.com


Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Krzysztof Wilczyński <kw@linux.com>