snd-firewire-lib: fix no sound in blocking mode for BeBoB based devices.

In IEC 61883-6, there is a FDF special format for NO-DATA pcaket. This can be
applied to blocking mode and not to non-blocking mode.

If AMDTP transmitter hope to transmit a packet with no-data, it can use this
NO-DATA FDF but actually BeBoB based devices don't hope it. Then it transmits
NO-DATA packet with usual FDF and SYT which means no information.

This commit modifies transmitting process according to this.