ACPI: utils: Make acpi_handle_path() not static

acpi_handle_path() will soon be required for node name comparison
elsewhere in ACPI framework. Remove the static keyword and add the
prototype to include/linux/acpi.h.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>