alsa: rework buffer/period configuration

alsa: rework buffer/period configuration

- As discussed on alsa-devel it's probably better to initialize the
  buffer size first, followed by the period size. If that fails try the
  other way round. If that fails try to configure only buffer size. If
  that fails try to configure only period size. Finally, try to
  configure neither.

- Don't require integral periods anymore.

Both of these changes should help improving compatibility with various
weirder sound devices, such as TV cards.