This is mainly for RME RayDAT that has a fixed buffersize of 16k:
dev_name : hw:HDSPMxc2f6c5,0
channels : 36
min_rate : 32000
max_rate : 192000
min_bufz : 16384
max_bufz : 16384
min_nper : 4
max_nper : 512
However nperiod configuration determines the effective latency
regardless.
This is similar to https://github.com/jackaudio/jack1/blob/master/drivers/alsa/alsa_driver.c#L476-L486
buffer-size = periods * period-size
Previously, buffersize was used for period-size.
This fixes an issue with a dedicated .asoundrc configuring a specific
period-size or buffer-size that has to be exact.
Ardour's device configuration failed in this case.
This has not been an issues since most hardware devices offer a wide
range: 8 < period-size < 262144 ; 16 < buffer-size < 524288.
Only a subset of which (32 .8192) is allowed by Ardour.
