Gayle support reworked

[Radoslaw Kujawa <radoslaw.kujawa%c0ff33.net@localhost>]

Hi all.

I’ve reworked[1] the support for Gayle chip. This has implications for:
- A600/1200 internal IDE (wdc at mainbus)
- A4000 internal IDE (wdc at mainbus)
- FastATA 1200 Mk-III/Mk-IV (efa at mainbus)
- ACA500 Compact Flash (wdc at acafh)

I’d appreciate testing, as I couldn’t try all the possible configurations.

[1] chttp://mail-index.netbsd.org/source-changes/2014/01/03/msg050416.html

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Best regards,
Radoslaw Kujawa