sync: remove legacy sync info API

The legacy fence/pt info API has been deprecated for a while. This
change removes it from headers, so remaining users will have to switch
to the modern API when they're re-compiled. The functions are still
provided by libsync.so and tests remain, so existing binaries should
continue to work. Eventually these will be removed too, though, once
it's reasonable to expect those binaries to have been recompiled.

This reverts commit eed25df46a22a143a0341113759894c23a9b6cbf, which
reverted the previous attempt in commit
798ba95bda14f9f28561a2a27ba406537f8bb8a8 now that more users of the
legacy API have been converted.

Bug: 35326015
Test: make checkbuild
Test: adb shell dumpsys SurfaceFlinger --latency
diff --git a/libsync/sync.c b/libsync/sync.c
index 6b187fa..b8c48c7 100644
--- a/libsync/sync.c
+++ b/libsync/sync.c
@@ -30,6 +30,29 @@
 
 #include <android/sync.h>
 
+/* Prototypes for deprecated functions that used to be declared in the legacy
+ * android/sync.h. They've been moved here to make sure new code does not use
+ * them, but the functions are still defined to avoid breaking existing
+ * binaries. Eventually they can be removed altogether.
+ */
+struct sync_fence_info_data {
+    uint32_t len;
+    char name[32];
+    int32_t status;
+    uint8_t pt_info[0];
+};
+struct sync_pt_info {
+    uint32_t len;
+    char obj_name[32];
+    char driver_name[32];
+    int32_t status;
+    uint64_t timestamp_ns;
+    uint8_t driver_data[0];
+};
+struct sync_fence_info_data* sync_fence_info(int fd);
+struct sync_pt_info* sync_pt_info(struct sync_fence_info_data* info, struct sync_pt_info* itr);
+void sync_fence_info_free(struct sync_fence_info_data* info);
+
 /* Legacy Sync API */
 
 struct sync_legacy_merge_data {