arm64: dts: msm8996: Drop model

DTS board files should always specify model and compatible.

All DTS board files that includes msm8996.dtsi
already specifies model and compatible, and will thus
override the model and compatible in msm8996.dtsi.

Drop model from msm8916.dtsi, since it is only a source of confusion.

Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>