kernfs: Drop unnecessary "mutex" local variable initialization

These are unnecessary and unconventional. Remove them. Also move variable
declaration into the block that it's used. No functional changes.

Cc: Imran Khan <imran.f.khan@oracle.com>
Tested-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220828050440.734579-3-tj@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/kernfs/file.c

@@ -555,7 +555,7 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
 				struct kernfs_open_file *of)
 {
 	struct kernfs_open_node *on, *new_on = NULL;
-	struct mutex *mutex = NULL;
+	struct mutex *mutex;
 
 	mutex = kernfs_open_file_mutex_lock(kn);
 	on = kernfs_deref_open_node_locked(kn);
@@ -599,7 +599,7 @@ static void kernfs_unlink_open_file(struct kernfs_node *kn,
 				 struct kernfs_open_file *of)
 {
 	struct kernfs_open_node *on;
-	struct mutex *mutex = NULL;
+	struct mutex *mutex;
 
 	mutex = kernfs_open_file_mutex_lock(kn);
 
@@ -776,9 +776,10 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
 {
 	struct kernfs_node *kn = inode->i_private;
 	struct kernfs_open_file *of = kernfs_of(filp);
-	struct mutex *mutex = NULL;
 
 	if (kn->flags & KERNFS_HAS_RELEASE) {
+		struct mutex *mutex;
+
 		mutex = kernfs_open_file_mutex_lock(kn);
 		kernfs_release_file(kn, of);
 		mutex_unlock(mutex);
@@ -796,7 +797,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
 {
 	struct kernfs_open_node *on;
 	struct kernfs_open_file *of;
-	struct mutex *mutex = NULL;
+	struct mutex *mutex;
 
 	if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
 		return;