device property: Introduce fwnode_device_is_available()

Add fwnode_device_is_available() to tell whether the device corresponding
to a certain fwnode_handle is available for use.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>