Add a metadata field to BufferDesc

This change adds a variable-length metadata field to BufferDesc.  This
new data is owned by EVS Camera HAL implementations and opaque to EVS
manager.

Change-Id: If9b25093afa55ea0782af776a3f67923664e0058
Fix: 142891952
Bug: 142888671
Test: Build successful
Signed-off-by: Changyeon Jo <changyeon@google.com>
diff --git a/automotive/evs/1.1/types.hal b/automotive/evs/1.1/types.hal
index f88d223..aafdb70 100644
--- a/automotive/evs/1.1/types.hal
+++ b/automotive/evs/1.1/types.hal
@@ -69,6 +69,8 @@
      * Time that this buffer is being filled.
      */
     int64_t timestamp;
+
+    vec<uint8_t> metadata;
 };
 
 /**