Skip AV1E_SET_TILE_COLUMNS if value is the default

The default value of AV1E_SET_TILE_COLUMNS is 0. Skip the
aom_codec_control(AV1E_SET_TILE_COLUMNS) call if the value we want to
set it to is 0, because the update_extra_cfg() call after setting the
value is not that cheap.

Also cast the return value of log2() to unsigned int because that is the
parameter type of AV1E_SET_TILE_COLUMNS.

Remove the aom_codec_control(&codec, AV1E_SET_ROW_MT, 1) call. 1 is the
default value of AV1E_SET_ROW_MT.

Change-Id: Ie7d066865b12b8766f4d4798a914f1c573f60ba2

examples/svc_encoder_rtc.c

diff --git a/examples/svc_encoder_rtc.c b/examples/svc_encoder_rtc.c
index 7b1056d..eb336d5 100644
--- a/examples/svc_encoder_rtc.c
+++ b/examples/svc_encoder_rtc.c
@@ -1410,9 +1410,10 @@
   aom_codec_control(&codec, AV1E_SET_ENABLE_FILTER_INTRA, 0);
   aom_codec_control(&codec, AV1E_SET_INTRA_DEFAULT_TX_ONLY, 1);
 
-  aom_codec_control(&codec, AV1E_SET_TILE_COLUMNS,
-                    cfg.g_threads ? (int)log2(cfg.g_threads) : 0);
-  if (cfg.g_threads > 1) aom_codec_control(&codec, AV1E_SET_ROW_MT, 1);
+  if (cfg.g_threads > 1) {
+    aom_codec_control(&codec, AV1E_SET_TILE_COLUMNS,
+                      (unsigned int)log2(cfg.g_threads));
+  }
 
   aom_codec_control(&codec, AV1E_SET_TUNE_CONTENT, app_input.tune_content);
   if (app_input.tune_content == AOM_CONTENT_SCREEN) {