bus: fsl-mc: fix mmio base address for child DPRCs

Some versions of the MC firmware wrongly report 0 for register base
address of the DPMCP associated with child DPRC objects thus rendering
them unusable. This is particularly troublesome in ACPI boot scenarios
where the legacy way of extracting this base address from the device
tree does not apply.
Given that DPMCPs share the same base address, workaround this by using
the base address extracted from the root DPRC container.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Link: https://lore.kernel.org/r/20210715140718.8513-8-laurentiu.tudor@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>