The specific power domain can't be used in a way provided by the commit
01ac170b, i.e. pointer to platform device is a subject to change during
unbound / bind cycle.

This reverts commit 01ac170b.

Fixes: 3df2da96 (Revert "ACPI / LPSS: introduce a 'proxy' device to power on LPSS for DMA")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>