firewire: move fw_device() and fw_unit() to use container_of_const()

The driver core is changing to pass some pointers as const, so move
fw_device() and fw_unit() functions to use container_of_const() to
handle this change.

fw_device() and fw_unit() now properly keeps the const-ness of the
pointer passed into it, while as before it could be lost.

This also required turning fw_parent_device() into a macro to preserve
the const-ness of the pointer passed into it if necessary.

Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230111113018.459199-5-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/firewire.h

@@ -208,10 +208,7 @@ struct fw_device {
 	struct fw_attribute_group attribute_group;
 };
 
-static inline struct fw_device *fw_device(struct device *dev)
-{
-	return container_of(dev, struct fw_device, device);
-}
+#define fw_device(dev)	container_of_const(dev, struct fw_device, device)
 
 static inline int fw_device_is_shutdown(struct fw_device *device)
 {
@@ -229,10 +226,7 @@ struct fw_unit {
 	struct fw_attribute_group attribute_group;
 };
 
-static inline struct fw_unit *fw_unit(struct device *dev)
-{
-	return container_of(dev, struct fw_unit, device);
-}
+#define fw_unit(dev)	container_of_const(dev, struct fw_unit, device)
 
 static inline struct fw_unit *fw_unit_get(struct fw_unit *unit)
 {
@@ -246,10 +240,7 @@ static inline void fw_unit_put(struct fw_unit *unit)
 	put_device(&unit->device);
 }
 
-static inline struct fw_device *fw_parent_device(struct fw_unit *unit)
-{
-	return fw_device(unit->device.parent);
-}
+#define fw_parent_device(unit)	fw_device(unit->device.parent)
 
 struct ieee1394_device_id;