[spatial svc] Remove vpx_svc_parameters_t and the loop that sets it for each layer

[spatial svc] Remove vpx_svc_parameters_t and the loop that sets it for each layer

vpx_svc_parameters_t contains id, resolution and min/max qp for each spatial layer.

In this change we will use extra config to send min/max qp and scaling factors, then calculate layer resolution inside encoder.

Change-Id: Ib673303266605fe803c3b067284aae5f7a25514a