The ranges parent bus address may just be a tag to the entry in the parent
node. Take this in to account by searching until we find the range for the
root node.

Differential Revision:	https://reviews.freebsd.org/D1160
Reviewed by:	ian
Obtained from:	ABT Systems Ltd
Sponsored by:	The FreeBSD Foundation
Add L2-cache writeback/flush operations. Supported 32,128-byte line-size,
else ignored. Cavium Networks also ignored as it has non-standard config
registers.

Obtained from:	NetBSD
Sponsored by:	DARPA, AFRL