MFC:

MFC:
	Add support for working around controllers that cannot do DMA in 48bit.
	The workaround use PIO mode above ~137GB to allow using the disk.
	Add the Acer chips with rev < 0xc4 as first candidate.

	Add support for the Promise PDC4071[89] chips on the Fasttrak TX4300.
	Docs kindly provided by Promise.

	Apply fix for "pr82261 DMA-support on Sparc64 broken"

	Use the bio field instead of the driver field as intended.

	Dont set default mode to ATA_DMA_MAX on devices not capable of DMA.

Approved by: re@ (scottl)