libata: Fix ata_busy_wait() kernel docs

> Looks like you should use ata_busy_wait() here, rather than reproducing
> the same code again.

It waits in 10uS chunks while 1uS chunks were used in the workaround.
Could indeed do that once I know the fix is right. While I'm at it the
ata_busy_wait kerneldoc is borked so here's a fix

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

include/linux/libata.h

@@ -1054,6 +1054,8 @@ static inline void ata_pause(struct ata_port *ap)
 /**
  *	ata_busy_wait - Wait for a port status register
  *	@ap: Port to wait for.
+ *	@bits: bits that must be clear
+ *	@max: number of 10uS waits to perform
  *
  *	Waits up to max*10 microseconds for the selected bits in the port's
  *	status register to be cleared.