msm: camera: smmu: Set the segment size for the context banks

Set the right segment size in the driver for dma_map_sg to
allow for partial cache maintanence.

Change-Id: I6c439f23e957eb667bf959c830b120c0390e41b1
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>
Signed-off-by: Jigarkumar Zala <jzala@codeaurora.org>