crash in EVS decoder at 48 kHz

When running the EVS decoder at 48 kHz, it crashes in the HQ core due to the short length of buffer synth[].

The issue can be observed after SHA-1: ebf10d0b and is related to the missing use of function delay_signal().

I will revisit the use of delay_signal() in BASOP such that it matches its use in FLP.