[PATCH] spufs: fix local store page refcounting

With the new rules for reserved pages, the spufs now
needs working page reference counting.

I should probably look into converting to vm_insert_page,
but for now this patch makes spufs work again.

Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>