Add an implementation of the SCM interface that works on ARM64 SoCs.  This
is used by things like determine if we have HDCP support or not on the
system.
Signed-off-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>