Enable motion field estimation in DRL

Enable the use of motion field estimation in the dynamic motion
vector referencing system. With default experiments on, it improves
the compression performance:

lowres 1.2%
midres 1.5%

Change-Id: Ifc5b15a7239b5c3212ea50f326ab99d372034658
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 18663cc..7af5c0e 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -5287,6 +5287,7 @@
 
 #if CONFIG_MFMV
   av1_setup_frame_buf_refs(cm);
+  av1_setup_motion_field(cm);
 #endif
 
   av1_setup_block_planes(xd, cm->subsampling_x, cm->subsampling_y);