acpi: refactor pxb crs computation

acpi: refactor pxb crs computation

Instead of always passing both IO and MEM ranges when
computing CRS ranges, define a new CrsRangeSet structure
that include them both.

This is done before introducing a third type of range,
64-bit MEM, so it will be easier to pass them all around.

Reviewed-by: Igor Mammedov <[email protected]>
Signed-off-by: Marcel Apfelbaum <[email protected]>
Tested-by: Laszlo Ersek <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>