powerpc: Fix 64K page size support for PPC44x

PPC44x supports page sizes other than 4K however when 64K page sizes
are selected compilation fails. This is due to a change in the
definition of pgtable_t introduced by the following patch:

commit 5c1f6ee9a31cbdac90bbb8ae1ba4475031ac74b4
Author: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
powerpc: Reduce PTE table memory wastage

The above patch only implements the new layout for PPC64 so it doesn't
compile for PPC32 with a 64K page size. Ideally we should implement
the same layout for PPC32 however for the meantime this patch reverts
the definition of pgtable_t for PPC32.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/page.h

@@ -403,7 +403,7 @@ void arch_free_page(struct page *page, int order);
 
 struct vm_area_struct;
 
-#ifdef CONFIG_PPC_64K_PAGES
+#if defined(CONFIG_PPC_64K_PAGES) && defined(CONFIG_PPC64)
 typedef pte_t *pgtable_t;
 #else
 typedef struct page *pgtable_t;