ARM: dts: msm: Add v4l2 rotator node to msm8996

Add mdss_rotator node with smmu subnodes.

Change mdss_mdp to interrupt controller so rotator can receive interrupt
routed by mdp handler.

Also, reserve control 4 and writeback 0/1 and their associated mixers
for v4l2 rotator driver.

CRs-Fixed: 1017182
Change-Id: I32f312f11fcbebbff0799120448d6e8f0d9ec98d
Signed-off-by: Alan Kwong <akwong@codeaurora.org>