Removal of duplicate session check with fastrpc_session_exists API as
it is no longer needed. Duplicate session creation is restricted using
set_session_info flag already.
Change-Id: I6b85d96f85e8d1e5af005a6939d8b9a25ca06fcf
Signed-off-by: Ansa Ahmed <quic_ansa@quicinc.com>