ACPI / LPSS: override SDIO private register space size from ACPI tables

The SDIO device in Lynxpoint has its LTR registers reserved for a
WiFi device (a child of the SDIO device) in the ACPI namespace even
though those registers physically belong to the SDIO device itself.
In order to be able to access the SDIO LTR registers from the ACPI
LPSS driver for diagnostic purposes we need to use a size override
for the SDIO private register space.

Add a possibility to override the size of the private register space
of an LPSS device provided by the ACPI tables in the ACPI LPSS driver
and set the correct size for the SDIO device in there.

[rjw: Changelog]
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>