gui: CpuConsumer::lockNextBuffer change return code when too many bufs acquired

- Return NOT_ENOUGH_DATA instead of INVALID_OPERATION when too many
  buffers have already been locked.
- INVALID_OPERATION is nominally used when something irrecoverable happens,
  but in this case the client just needs to call unlockBuffer to go back into a
  good state.

Bug: 10333400
Change-Id: I3a034d77de85741429f832a90eedd670afa1dc94
diff --git a/include/gui/CpuConsumer.h b/include/gui/CpuConsumer.h
index 9290676..6f4c2ec 100644
--- a/include/gui/CpuConsumer.h
+++ b/include/gui/CpuConsumer.h
@@ -90,7 +90,7 @@
     // Gets the next graphics buffer from the producer and locks it for CPU use,
     // filling out the passed-in locked buffer structure with the native pointer
     // and metadata. Returns BAD_VALUE if no new buffer is available, and
-    // INVALID_OPERATION if the maximum number of buffers is already locked.
+    // NOT_ENOUGH_DATA if the maximum number of buffers is already locked.
     //
     // Only a fixed number of buffers can be locked at a time, determined by the
     // construction-time maxLockedBuffers parameter. If INVALID_OPERATION is