ACPI: bus: Refactor ACPI matching functions for better readability

With temporary variables for OF and ACPI IDs, it's easier to read
the code. No functional change intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>