PCI: imx6: Limit DBI register length for imx6qp PCIe

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 8528d1228ca7 ("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>