This ensures offsets will not be truncated on large files on i686.
Port UCHI, AC97, SB16, BMIDEChannel and AHCIPort to use the helper to allocate DMA buffers.
u16
Executing `asctl set r 96000` no longer results in weird sample rates being set on the audio devices. SB16 checks for a sample rate between 1 and 44100 Hz, while AC97 implements double-rate support which allows sample rates between 8kHz and 96kHZ.