Use the correct device as the power_for_sleep() method
always pass request up to parent bridge.

Reviewed by:	jhb
MFC after:	1 week
xMFC:		r274386,r274397


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274635 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f