Add tomstone proto support for riscv64

Signed-off-by: Liu Cunyuan <liucunyuan.lcy@linux.alibaba.com>
Signed-off-by: Mao Han <han_mao@linux.alibaba.com>
Change-Id: Ie22c2895fc30fab68eddc18713c80e403f44b203
diff --git a/debuggerd/proto/tombstone.proto b/debuggerd/proto/tombstone.proto
index f0d3d3f..49865a2 100644
--- a/debuggerd/proto/tombstone.proto
+++ b/debuggerd/proto/tombstone.proto
@@ -48,8 +48,9 @@
   ARM64 = 1;
   X86 = 2;
   X86_64 = 3;
+  RISCV64 = 4;
 
-  reserved 4 to 999;
+  reserved 5 to 999;
 }
 
 message Signal {