kernfs: remove redundant kernfs_rwsem declaration.

Since 'commit 393c3714081a ("kernfs: switch global kernfs_rwsem lock to
per-fs lock")' per-fs kernfs_rwsem has replaced global kernfs_rwsem.
Remove redundant declaration of global kernfs_rwsem.

Fixes: 393c3714081a ("kernfs: switch global kernfs_rwsem lock to per-fs lock")
Signed-off-by: Imran Khan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

fs/kernfs/kernfs-internal.h

···
 /*
  * dir.c
  */
-extern struct rw_semaphore kernfs_rwsem;
 extern const struct dentry_operations kernfs_dops;
 extern const struct file_operations kernfs_dir_fops;
 extern const struct inode_operations kernfs_dir_iops;