AESinkALSA: Set correct value for AES3 when using HBR mode

According to the HDMI 1.4a document, the only acceptable value
for AES3 in HBR mode is 0x09, which corresponds to a frame rate
of 768000. Some sinks or drivers ignore this, but some do not.
AESinkALSA: Allow fragmentation, e.g. even multiply of PeriodSize