msm: cpp: Attach/detach iommu device on open/close node

Change the iommu device attachement to happen on
cpp_open_node and detachment in cpp_close_node.
It decrease the power consumption when Camera is not
working.

Change-Id: I661e92e1cea294d0333e1376d7f5cdfc7cd1c2e8
Signed-off-by: Iliya Varadzhakov <ivarad@codeaurora.org>