migration: rename 'file' in MigrationState to 'to_dst_file'

Rename the 'file' member of MigrationState to 'to_dst_file' to
be consistent with to_src_file, from_src_file and from_dst_file.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Message-Id: <1452829066-9764-3-git-send-email-zhang.zhanghailiang@huawei.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
diff --git a/migration/rdma.c b/migration/rdma.c
index 86a13b8..bcae1e8 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -3504,7 +3504,7 @@
 
     trace_rdma_start_outgoing_migration_after_rdma_connect();
 
-    s->file = qemu_fopen_rdma(rdma, "wb");
+    s->to_dst_file = qemu_fopen_rdma(rdma, "wb");
     migrate_fd_connect(s);
     return;
 err: