[PATCH] Enhanced SiS96x support

[PATCH] Enhanced SiS96x support

This is an update for the SiS IDE driver.

This is a 99% Vojtech work :
- Independant southbridge detection (no need to add current and future
  MuTIOL northbridge PCI ids knowledge to the driver),
- Lots of code cleanup,
- Debug code removed (unused for a while, I will maintain it in my tree
  if needed),

I changed some things:
- the new config_xfer_rate is commented out until ide_find_best_mode is
  patched for bad drive handling (until then I reverted to the old one
  using the config_drive_xfer_rate helper function).