hugetlbfs: remove unregister_filesystem() when initializing module

hugetlbfs: remove unregister_filesystem() when initializing module

It was introduced by d1d5e05ffd ("hugetlbfs: return error code when
initializing module") but as Al pointed out, is a bad idea.

Quoted comments from Al.
Note that unregister_filesystem() in module init is *always* wrong; it's not
an issue here (it's done too early to care about and realistically the box
is not going anywhere - it'll panic when attempt to exec /sbin/init fails,
if not earlier), but it's a damn bad example.

Consider a normal fs module.  Somebody loads it and in parallel with that
we get a mount attempt on that fs type.  It comes between register and
failure exits that causes unregister; at that point we are screwed since
grabbing a reference to module as done by mount is enough to prevent
exit, but not to prevent the failure of init.  As the result, module will
get freed when init fails, mounted fs of that type be damned.
end of quote

So remove it.

Signed-off-by: Hillf Danton <dhillf@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>