kernfs: remove redundant kernfs_rwsem declaration.

Since 'commit 393c3714 ("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: 393c3714 ("kernfs: switch global kernfs_rwsem lock to per-fs lock")
Signed-off-by: NImran Khan <imran.f.khan@oracle.com>
Link: https://lore.kernel.org/r/20220218010205.717582-1-imran.f.khan@oracle.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/kernfs/kernfs-internal.h

@@ -122,7 +122,6 @@ int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 /*
  * 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;