opengl: fix warning on non-Apple builds

TARGET_OS_IPHONE is not defined in most cases.

modules/video_output/opengl/display.c

@@ -190,7 +190,7 @@ static void PlacePicture(vout_display_t *vd, vout_display_place_t *place,
 static int Open(vout_display_t *vd,
                 video_format_t *fmt, vlc_video_context *context)
 {
-#if TARGET_OS_IPHONE
+#if defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE
     if (fmt->i_chroma == VLC_CODEC_CVPX_P010)
         return VLC_EGENERIC;
 #endif