msm: smem: Add new SMEM heap item for IPC FIFO

Add a new SMEM heap item for use by the IPC_FIFO module.

Change-Id: Ice0aa1e5aa8777be48494d5c76634332e32094a5
Acked-by: Kaushik Sikdar <ksikdar@qti.qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>