msm: ADSPRPC: Validate the SMMU session count

Make sure that the session count does not exceed the maximum
sessions to avoid buffer overflow.

Change-Id: I1a9830a6f859d7d525247d27d0a143997998d997
Acked-by: Bharath Kumar <bkumar@qti.qualcomm.com>
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>