msm: mdss: correct initialization of iommu domain for mdp3

Currently both the iommu domains are initialized to
non-secure domains, which is causing XPU violation
during boot up. This change ensures proper initialization
of iommu domain in 8909 mdp3 driver.

Change-Id: Ic47052aca948c862a88336c455e54986cb772408
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>