dwarf_reg_pool and dwarf_frame_pool are not properly destroyed when
cleaning up the dwarf unwinder.  Destroy them with mempool_destroy().

Also mark dwarf_unwinder_cleanup() as __init.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>