powerpc/mm: Use PAGE_FACTOR

PAGE_FACTOR was defined to reflect the difference between configured
page size and fixed 4KB page size. Replace (PAGE_SHIFT - HW_PAGE_SHIFT)
with PAGE_FACTOR.
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hash_low_64.S

@@ -514,7 +514,7 @@ htab_insert_pte:
 	andis.	r0,r31,_PAGE_4K_PFN@h
 	srdi	r5,r31,PTE_RPN_SHIFT
 	bne-	htab_special_pfn
-	sldi	r5,r5,PAGE_SHIFT-HW_PAGE_SHIFT
+	sldi	r5,r5,PAGE_FACTOR
 	add	r5,r5,r25
 htab_special_pfn:
 	sldi	r5,r5,HW_PAGE_SHIFT
@@ -544,7 +544,7 @@ htab_call_hpte_insert1:
 	andis.	r0,r31,_PAGE_4K_PFN@h
 	srdi	r5,r31,PTE_RPN_SHIFT
 	bne-	3f
-	sldi	r5,r5,PAGE_SHIFT-HW_PAGE_SHIFT
+	sldi	r5,r5,PAGE_FACTOR
 	add	r5,r5,r25
 3:	sldi	r5,r5,HW_PAGE_SHIFT