msm/sde/rotator: add check for vbif dt properties

Add check in rotator for vbif properties that are not present
in dt to avoid error msgs in bootup.

Change-Id: I68280572cff92a4e0c86a92f376ef6f1e0acadff
Signed-off-by: Shubhashree Dhar <dhar@codeaurora.org>