arch/sh/kernel/dwarf.c: use mempool_create_slab_pool()

Mempools created for slab caches should use mempool_create_slab_pool().

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>