msm: mdss: attach iommu dynamically for video mode panel

MDSS driver supports iommu dynamic attach only when splash
thread is enabled. Client might want to attach the iommu
dynamically without using splash thread to avoid blink for
video mode panel. That is possible by doing 1-to-1 memory
mapping before iommu attach and splash memory late release.
This change supports the dynamic memory mapping to avoid
splash thread. Release the splash memory in first commit
instead of first suspend resume.

CRs-fixed: 755804
Change-Id: I7dcb415644a54a4b80f700c4d0914511a5685830
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>