hwc: fix compilation issue on backport of Ieb91b70 [DO NOT MERGE]

Fixes compilation issue for backport of the following patch:

	commit 6e69a5311599cc90b654031e93b272017169f1e0
	Author: Arun Kumar K.R <akumarkr@codeaurora.org>
	Date:   Wed Jun 5 17:21:38 2013 -0700

	hwc: Fix to avoid heap corruption

Bug: 24163261

Change-Id: I4d8d02bf75e7914c2c5c4f9c2b4ea047481b302c
Signed-off-by: Patrick Tjin <pattjin@google.com>