kernfs: remove unneeded #if 0 guard

Commit f2eb478f ("kernfs: move struct kernfs_root out of the public
view.") moved kernfs_root out of kernfs.h, but my debugging code of a
 #if 0 was left in accidentally.  Fix that up by removing the guards.

Fixes: f2eb478f ("kernfs: move struct kernfs_root out of the public view.")
Cc: Tejun Heo <tj@kernel.org>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20220318073452.1486568-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>