misc: fastrpc: Add fdlist implementation

Add fdlist implementation to support dma handles. fdlist is populated by
DSP if any map is no longer used and it is freed during put_args.

Signed-off-by: Vamsi Krishna Gattupalli <quic_vgattupa@quicinc.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>