ATAng panic: ATAFD re-using freed memory

[Nate Lawson]

With a fresh checkout of last night's -current, I cannot boot my laptop.
ATAFD panics the box by reusing freed memory.  I do not have a floppy
drive in the laptop and when I do, it's a legacy floppy, not atapi.  Here
are the messages:

[normal ad0/acd0 probe message]
afd0: timeout waiting for ATAPI ready
afd0: timeout waiting for ATAPI ready
afd0: timeout waiting for ATAPI ready
afd0: timeout waiting for ATAPI ready
afd0: timeout waiting for ATAPI ready
panic: Memory modified after free: 0xc33ed400 (252)
Most recently used by AFD driver

A working dmesg:
http://www.root.org/~nate/acpi/ibm.dmesg

-Nate