[PATCH] powerpc: Fix warning in add_memory

arch/powerpc/mm/mem.c: In function `add_memory':
arch/powerpc/mm/mem.c:128: warning: assignment makes integer from pointer without a cast

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>