Exclude gop_structure.{c,h} from CONFIG_REALTIME_ONLY

BUG=aomedia:2397

Change-Id: I8d01731d2285117489bd686165135c6005bbda7f
diff --git a/av1/av1.cmake b/av1/av1.cmake
index 0fe5bc4..ce9af78 100644
--- a/av1/av1.cmake
+++ b/av1/av1.cmake
@@ -370,6 +370,8 @@
   list(REMOVE_ITEM AOM_AV1_ENCODER_SOURCES
                    "${AOM_ROOT}/av1/encoder/firstpass.c"
                    "${AOM_ROOT}/av1/encoder/firstpass.h"
+                   "${AOM_ROOT}/av1/encoder/gop_structure.c"
+                   "${AOM_ROOT}/av1/encoder/gop_structure.h"
                    "${AOM_ROOT}/av1/encoder/pass2_strategy.c"
                    "${AOM_ROOT}/av1/encoder/mbgraph.c"
                    "${AOM_ROOT}/av1/encoder/mbgraph.h"