qcow2: fix the macro QCOW_MAX_L1_SIZE's use

QCOW_MAX_L1_SIZE's unit is byte, and l1_size's unit
is l1 table entry size(8 bytes).
Signed-off-by: NWen Congyang <wency@cn.fujitsu.com>
Message-id: 54FFB0F1.5010307@cn.fujitsu.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/qcow2-snapshot.c

@@ -702,7 +702,7 @@ int qcow2_snapshot_load_tmp(BlockDriverState *bs,
     sn = &s->snapshots[snapshot_index];
 
     /* Allocate and read in the snapshot's L1 table */
-    if (sn->l1_size > QCOW_MAX_L1_SIZE) {
+    if (sn->l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) {
         error_setg(errp, "Snapshot L1 table too large");
         return -EFBIG;
     }

block/qcow2.c

@@ -742,7 +742,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     /* read the level 1 table */
-    if (header.l1_size > QCOW_MAX_L1_SIZE) {
+    if (header.l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) {
         error_setg(errp, "Active L1 table too large");
         ret = -EFBIG;
         goto fail;