having figured out the sample rate issue with the ESS1869 (don't use 4
bytes/DMA request mode) the code will now automatically use ESS
extensions if ESS1869 chipset is detected.
update sample rate limits of ESS chipset
bugfix: if ESS chipset, assume 16-bit DMA channel is the same as the
8-bit DMA channel, even if we had to probe the IRQ and DMA channels
manually.