Avoid #if inside macro arguments

Visual Studio doesn't support it.

Change-Id: Ie7bd21e6d9a8a30b7b89e9fca6b82dd2aa406a89
diff --git a/aomenc.c b/aomenc.c
index 3d82e15..053db22 100644
--- a/aomenc.c
+++ b/aomenc.c
@@ -638,10 +638,8 @@
   int arg_ctrls[ARG_CTRL_CNT_MAX][2];
   int arg_ctrl_cnt;
   int write_webm;
-#if CONFIG_HIGHBITDEPTH
   // whether to use 16bit internal buffers
   int use_16bit_internal;
-#endif
 };
 
 struct stream_state {
@@ -1802,11 +1800,8 @@
         }
       }
       if (stream->config.cfg.g_profile > 1) {
-#if CONFIG_HIGHBITDEPTH
+        if (!CONFIG_HIGHBITDEPTH) fatal("Unsupported profile.");
         stream->config.use_16bit_internal = 1;
-#else
-        fatal("Unsupported profile.");
-#endif
       }
       if (profile_updated && !global.quiet) {
         fprintf(stderr,