ceph: do_sync is never initialized

Probably this code was syncing a lot more often then intended because
the do_sync variable wasn't set to zero.

Cc: stable@vger.kernel.org # v3.11+
Fixes: c62988ec0910 ('ceph: avoid meaningless calling ceph_caps_revoking if sync_mode == WB_SYNC_ALL.')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>

fs/ceph/addr.c

@@ -689,7 +689,7 @@ static int ceph_writepages_start(struct address_space *mapping,
 	int rc = 0;
 	unsigned wsize = 1 << inode->i_blkbits;
 	struct ceph_osd_request *req = NULL;
-	int do_sync;
+	int do_sync = 0;
 	u64 truncate_size, snap_size;
 	u32 truncate_seq;