Private info for specified board
Channel whose sample rate will be adjusted
New sample rate, in Khz
Helper function for the SNDCTL_DSP_SPEED ioctl. OSS semantics demand that all audio operations halt (if they are not already halted) when the SNDCTL_DSP_SPEED is given.
This function halts all audio operations for the given channel chan, and then calls via_set_rate to set the audio hardware to the new rate.