firewire: core: adds constant qualifier for local helper functions

Some local functions just handles given argument as mutable, thus it is
preferable to add constant qualifier to them.

Link: https://lore.kernel.org/r/20231221134849.603857-2-o-takashi@sakamocchi.jpSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-device.c

@@ -171,7 +171,7 @@ static const struct ieee1394_device_id *unit_match(struct device *dev,
 	return NULL;
 }
 
-static bool is_fw_unit(struct device *dev);
+static bool is_fw_unit(const struct device *dev);
 
 static int fw_unit_match(struct device *dev, struct device_driver *drv)
 {
@@ -679,7 +679,7 @@ static struct device_type fw_unit_type = {
 	.release	= fw_unit_release,
 };
 
-static bool is_fw_unit(struct device *dev)
+static bool is_fw_unit(const struct device *dev)
 {
 	return dev->type == &fw_unit_type;
 }
@@ -835,7 +835,7 @@ static struct device_type fw_device_type = {
 	.release = fw_device_release,
 };
 
-static bool is_fw_device(struct device *dev)
+static bool is_fw_device(const struct device *dev)
 {
 	return dev->type == &fw_device_type;
 }