kernfs: fix reference to renamed function

commit c637b8a ("kernfs:
 s/sysfs/kernfs/ in internal functions and whatever is left")
renamed kernfs_file_open to kernfs_fop_open, but didn't update the
comment referencing it.

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/4f2wybrepigxjpuxj4bdkh3qmksetfioedit2bdrswf6b75ebb@tarta.nabijaczleweli.xyz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: nabijaczleweli

fs/kernfs/file.c

@@ -447,7 +447,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 	 * warnings and we don't want to add spurious locking dependency
 	 * between the two.  Check whether mmap is actually implemented
 	 * without grabbing @of->mutex by testing HAS_MMAP flag.  See the
-	 * comment in kernfs_file_open() for more details.
+	 * comment in kernfs_fop_open() for more details.
 	 */
 	if (!(of->kn->flags & KERNFS_HAS_MMAP))
 		return -ENODEV;