adsprpc: Modify Remote scalars call backward compatible

Add proper remote scalar calls to get TZ security key, which compatible
with all dsp process groups TZ secure channel call.

Change-Id: I89663a50e27cdfb73e2c919235c44ec2643fc159
Acked-by: Tadakamalla Krishnaiah <ktadakam@qti.qualcomm.com>
Signed-off-by: Mohammed Nayeem Ur Rahman <mohara@codeaurora.org>