fbdev: mdp3: change iommu map sequence for cont splash

smmu fault occurs during boot up with continuous splash enabled
for video mode panels. Before smmu mapping set the attributes
with EARLY_MAP flag and then attach the iommu map.
This will ensure PA=VA mapping works fine.

Change-Id: I3c3d97997f67ac11c24e6079899b236e9217c4f3
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>