ACPI: utils: Add acpi_evaluate_reg() helper

With a recent fix to the pinctrl-cherryview driver we now have
2 drivers open-coding the parameter building / passing for calling
_REG on an ACPI handle.

Add a helper for this, so that these 2 drivers can be converted to this
helper.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>