powerpc/mm: Move THP headers around

We support THP only with book3s_64 and 64K page size. Move
THP details to hash64-64k.h to clarify the same.

Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 3967e3c..d42dd28 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -359,7 +359,7 @@
 struct page *pmd_page(pmd_t pmd)
 {
 	if (pmd_trans_huge(pmd) || pmd_huge(pmd))
-		return pfn_to_page(pmd_pfn(pmd));
+		return pte_page(pmd_pte(pmd));
 	return virt_to_page(pmd_page_vaddr(pmd));
 }