[SCSI] eata_pio: Clean up proc handling, bracketing and use cpu_relax()

So its ancient, its crap, but it kept showing up in my scans for stuff
that wanted fixing...

- Redo the proc code to be far cleaner
- Clean various return (0) type constructs
- Use cpu_relax()

The various waits ought to time out but thats another issue and probably
not worth solving.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>