powerpc/mm/hash: Free the subpage_prot_table correctly

Fixes: dad6f37c2602e ("powerpc: subpage_protect: Increase the array size to take care of 64TB")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Tested-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/subpage-prot.c

@@ -36,7 +36,7 @@ void subpage_prot_free(struct mm_struct *mm)
 		}
 	}
 	addr = 0;
-	for (i = 0; i < 2; ++i) {
+	for (i = 0; i < (TASK_SIZE_USER64 >> 43); ++i) {
 		p = spt->protptrs[i];
 		if (!p)
 			continue;