Fix inconsistency in gm parameter write to bitstream

Before this change, gm parameters were being written to the
bitstream for all frames, but only read for inter only frames,
causing a bitstream error.

Change-Id: I63b8e2fdf6358e07cc00718de04cc399809bde37
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 77aee22..2b846e8 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -3536,10 +3536,10 @@
 #if CONFIG_SUPERTX
     if (!xd->lossless[0]) update_supertx_probs(cm, header_bc);
 #endif  // CONFIG_SUPERTX
-  }
 #if CONFIG_GLOBAL_MOTION
-  write_global_motion(cpi, header_bc);
+    write_global_motion(cpi, header_bc);
 #endif  // CONFIG_GLOBAL_MOTION
+  }
 #if CONFIG_ANS
   ans_write_init(&header_ans, data);
   buf_ans_flush(header_bc, &header_ans);