powerpc/mm: Use the correct pointer when setting a 2MB pte

When setting a 2MB pte, radix__map_kernel_page() is using the address

	ptep = (pte_t *)pudp;

Fix this conversion to use pmdp instead. Use pmdp_ptep() to do this
instead of casting the pointer.

Fixes: 2bfd65e ("powerpc/mm/radix: Add radix callbacks for early init routines")
Cc: stable@vger.kernel.org # v4.7+
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/pgtable-radix.c

@@ -65,7 +65,7 @@ int radix__map_kernel_page(unsigned long ea, unsigned long pa,
 		if (!pmdp)
 			return -ENOMEM;
 		if (map_page_size == PMD_SIZE) {
-			ptep = (pte_t *)pudp;
+			ptep = pmdp_ptep(pmdp);
 			goto set_the_pte;
 		}
 		ptep = pte_alloc_kernel(pmdp, ea);
@@ -90,7 +90,7 @@ int radix__map_kernel_page(unsigned long ea, unsigned long pa,
 		}
 		pmdp = pmd_offset(pudp, ea);
 		if (map_page_size == PMD_SIZE) {
-			ptep = (pte_t *)pudp;
+			ptep = pmdp_ptep(pmdp);
 			goto set_the_pte;
 		}
 		if (!pmd_present(*pmdp)) {