Camera: Clarify ERROR_REQUEST callback

Allow partial result to be generated in the case of ERROR_REQUEST.

Test: Build
Bug: 155353799
Change-Id: I6ade958cac773e854d669aec3caf99191a875ec7
diff --git a/camera/device/3.2/ICameraDeviceCallback.hal b/camera/device/3.2/ICameraDeviceCallback.hal
index dec3bd8..607502e 100644
--- a/camera/device/3.2/ICameraDeviceCallback.hal
+++ b/camera/device/3.2/ICameraDeviceCallback.hal
@@ -95,7 +95,8 @@
      * statuses must be STATUS_ERROR, and the result metadata must be an
      * empty buffer. In addition, notify() must be called with a ERROR_REQUEST
      * message. In this case, individual ERROR_RESULT/ERROR_BUFFER messages
-     * must not be sent.
+     * must not be sent. Note that valid partial results are still allowed
+     * as long as the final result metadata fails to be generated.
      *
      * Performance requirements:
      *