ACPI: utils: Return bool from acpi_evaluate_reference()

There are only 4 users of acpi_evaluate_reference() and none of them
actually cares about the reason why it fails.  All of them are only
interested in whether or not it is successful, so it can return a bool
value indicating that.

Modify acpi_evaluate_reference() as per the observation above and update
its callers accordingly so as to get rid of useless code and local
variables.

The observable behavior of the kernel is not expected to change after
this modification of the code.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>