powerpc/mm: Don't hardcode the hash pte slot shift

Use the #define instead of open-coding the same
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/hash-64k.h

@@ -94,7 +94,7 @@ static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
 {
 	if ((pte_val(rpte.pte) & _PAGE_COMBO))
 		return (rpte.hidx >> (index<<2)) & 0xf;
-	return (pte_val(rpte.pte) >> 12) & 0xf;
+	return (pte_val(rpte.pte) >> _PAGE_F_GIX_SHIFT) & 0xf;
 }
 
 #define __rpte_to_pte(r)	((r).pte)

arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -50,7 +50,7 @@
 #define __real_pte(e,p)		(e)
 #define __rpte_to_pte(r)	(__pte(r))
 #endif
-#define __rpte_to_hidx(r,index)	(pte_val(__rpte_to_pte(r)) >> 12)
+#define __rpte_to_hidx(r,index)	(pte_val(__rpte_to_pte(r)) >>_PAGE_F_GIX_SHIFT)
 
 #define pte_iterate_hashed_subpages(rpte, psize, va, index, shift)       \
 	do {							         \

arch/powerpc/include/asm/nohash/64/pgtable.h

@@ -121,7 +121,7 @@
 #define __real_pte(e,p)		(e)
 #define __rpte_to_pte(r)	(__pte(r))
 #endif
-#define __rpte_to_hidx(r,index)	(pte_val(__rpte_to_pte(r)) >> 12)
+#define __rpte_to_hidx(r,index)	(pte_val(__rpte_to_pte(r)) >> _PAGE_F_GIX_SHIFT)
 
 #define pte_iterate_hashed_subpages(rpte, psize, va, index, shift)       \
 	do {							         \