driver core / ACPI: Represent ACPI companions using fwnode_handle

Now that we have struct fwnode_handle, we can use that to point to
ACPI companions from struct device objects instead of pointing to
struct acpi_device directly.

There are two benefits from that.  First, the somewhat ugly and
hackish struct acpi_dev_node can be dropped and, second, the same
struct fwnode_handle pointer can be used in the future to point
to other (non-ACPI) firmware device node types.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Grant Likely <grant.likely@linaro.org>

include/acpi/acpi_bus.h

@@ -386,7 +386,8 @@ static inline bool is_acpi_node(struct fwnode_handle *fwnode)
 
 static inline struct acpi_device *acpi_node(struct fwnode_handle *fwnode)
 {
-	return fwnode ? container_of(fwnode, struct acpi_device, fwnode) : NULL;
+	return is_acpi_node(fwnode) ?
+		container_of(fwnode, struct acpi_device, fwnode) : NULL;
 }
 
 static inline struct fwnode_handle *acpi_fwnode_handle(struct acpi_device *adev)