FPMT: Enable frame parallel encode for AOM_VBR

This patch enables frame parallelism for AOM_VBR by
setting num_fp_contexts appropriately.

Change-Id: Ifcb343c4fa37513aacb5c6205b86fdfb3e0d63ba
diff --git a/av1/encoder/ethread.c b/av1/encoder/ethread.c
index 3205a2e..48df376 100644
--- a/av1/encoder/ethread.c
+++ b/av1/encoder/ethread.c
@@ -742,9 +742,9 @@
 // This function returns 1 if frame parallel encode is supported for
 // the current configuration. Returns 0 otherwise.
 static AOM_INLINE int is_fp_config(AV1_PRIMARY *ppi, AV1EncoderConfig *oxcf) {
-  // TODO(Mufaddal, Aasaipriya): Test and enable multi-tile, resize and vbr
-  // config.
-  if (oxcf->rc_cfg.mode != AOM_Q) {
+  // FPMT is enabled for AOM_Q and AOM_VBR.
+  // TODO(Mufaddal, Aasaipriya): Test and enable multi-tile and resize config.
+  if (oxcf->rc_cfg.mode == AOM_CBR || oxcf->rc_cfg.mode == AOM_CQ) {
     return 0;
   }
   if (ppi->use_svc) {