arm64: dts: qcom: msm8996: Disabled VFE SMMU

Initializing the SMMU trips a security violation, so disable the VFE
SMMU for now.

Fixes: f3442ab9

 ("arm64: dts: qcom: msm8996: Add VFE SMMU node")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>