linker: simpler encoding for SHT_RELR sections.

This change modifies the encoding used in SHT_RELR sections to a simpler
version that gives better results. This encoding was suggested by Andrew
Grieve and is described in this post on generic-abi@googlegroups.com:
    https://groups.google.com/d/msg/generic-abi/bX460iggiKg/Pi9aSwwABgAJ

Bug: None
Test: Built image for marlin, flashed on device, ran arm and
      aarch64 binaries containing '.relr.dyn' sections using
      the new encoding.

Change-Id: I266affe0fbad91dc375995985a221cb02499447b
diff --git a/linker/linker_soinfo.h b/linker/linker_soinfo.h
index cb607a9..447c7c3 100644
--- a/linker/linker_soinfo.h
+++ b/linker/linker_soinfo.h
@@ -310,6 +310,7 @@
   bool relocate(const VersionTracker& version_tracker, ElfRelIteratorT&& rel_iterator,
                 const soinfo_list_t& global_group, const soinfo_list_t& local_group);
   bool relocate_relr();
+  void apply_relr_reloc(ElfW(Addr) offset);
 
  private:
   // This part of the structure is only available