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: I7f8d65e14af2949d9512191459d313ac4d3fff9c
Signed-off-by: Iliya Varadzhakov <ivarad@codeaurora.org>