Enable vp8x encoder to recognize vp8 specific options

Change-Id: Ib309c8c0a6c7073b71f0e6d131028501cb241daf

ivfenc.c

@@ -758,7 +758,8 @@ int main(int argc, const char **argv_)
     /* Handle codec specific options */
 #if CONFIG_VP8_ENCODER
 
-    if (codec->iface == &vpx_codec_vp8_cx_algo)
+    if (codec->iface == &vpx_codec_vp8_cx_algo ||
+        codec->iface == &vpx_codec_vp8x_cx_algo)
     {
         ctrl_args = vp8_args;
         ctrl_args_map = vp8_arg_ctrl_map;