Don't export libogg symbols from libstagefright

Some of these are also exported from libvorbisidec (Tremolo), which
can lead to strange results and crashes when linking with both
libstagefright and libvorbisidec.
Not exporting these symbols also shaves a few kilobytes off the size
of libstagefright.so

Test: build, run

Change-Id: I1ee6deb4fff11ff66063648d7681a7e25f4a2b86
diff --git a/media/libstagefright/exports.lds b/media/libstagefright/exports.lds
index aabc233..06c4f19 100644
--- a/media/libstagefright/exports.lds
+++ b/media/libstagefright/exports.lds
@@ -505,4 +505,8 @@
         YUY2ToYRow_Any_NEON*;
         YUY2ToYRow_C;
         YUY2ToYRow_NEON*;
+        ogg_packet_*;
+        ogg_page_*;
+        ogg_stream_*;
+        ogg_sync_*;
 };