Support OPUS_SET_COMPLEXITY() for multistream decoder

OPUS_SET_COMPLEXITY() is already implemented in the decoder
for controlling deep PLC since commit
8d43b18

This commit makes it also available for the mulitstream decoder.

Author: Daniel Danzberger

src/opus_multistream_decoder.c

@@ -433,6 +433,7 @@ int opus_multistream_decoder_ctl_va_list(OpusMSDecoder *st, int request,
        case OPUS_GET_GAIN_REQUEST:
        case OPUS_GET_LAST_PACKET_DURATION_REQUEST:
        case OPUS_GET_PHASE_INVERSION_DISABLED_REQUEST:
+       case OPUS_GET_COMPLEXITY_REQUEST:
        {
           OpusDecoder *dec;
           /* For int32* GET params, just query the first stream */
@@ -507,6 +508,7 @@ int opus_multistream_decoder_ctl_va_list(OpusMSDecoder *st, int request,
        }
        break;
        case OPUS_SET_GAIN_REQUEST:
+       case OPUS_SET_COMPLEXITY_REQUEST:
        case OPUS_SET_PHASE_INVERSION_DISABLED_REQUEST:
        {
           int s;