fs/ntfs3: Fix a resource leak bug in wnd_extend()

commit d6831847 upstream.

Add put_bh() to decrease the refcount of 'bh' after the job
is finished, preventing a resource leak.

Fixes: 3f3b442b ("fs/ntfs3: Add bitmap")
Cc: stable@vger.kernel.org
Signed-off-by: Haoxiang Li <haoxiang_li2024@163.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>