ACPI / LPSS: allow to use specific PM domain during ->probe()

The LPSS DMA controller would like to use the specific PM domain callbacks
during early stage, namely in ->probe(). This patch moves the specific PM
domain assignment early to be accessible during a whole life time of the device
in the system.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Scott Ashcroft <scott.ashcroft@talk21.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>