msm: camera: smmu: Fix uninitialized read of region in SMMU

Uninitialized local variable region is passed to cam_mem_util_hw_va.
Fixed by initializing region with invalid value.

Change-Id: Ib4652d4bd7605b625effea49f4f64ee22ee92737
Signed-off-by: Trishansh Bhardwaj <tbhardwa@codeaurora.org>