Added a cmd for configuring number of video buffers for camera, if supported

o currently, only available in Camera2

Change-Id: Id9bf157496209af9be65d147e70aa4830158c88d
diff --git a/include/system/camera.h b/include/system/camera.h
index e4cacc5..7a4dd53 100644
--- a/include/system/camera.h
+++ b/include/system/camera.h
@@ -163,6 +163,17 @@
      * can silently finish itself or show a dialog.
      */
     CAMERA_CMD_PING = 9,
+
+    /**
+     * Configure the number of video buffers used for recording. The intended
+     * video buffer count for recording is passed as arg1, which must be
+     * greater than 0. This command must be sent before recording is started.
+     * This command returns INVALID_OPERATION error if it is sent after video
+     * recording is started, or the command is not supported at all. This
+     * command also returns a BAD_VALUE error if the intended video buffer
+     * count is non-positive or too big to be realized.
+     */
+    CAMERA_CMD_SET_VIDEO_BUFFER_COUNT = 10,
 };
 
 /** camera fatal errors */