Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

s,KOBJMETHOD_END,DEVMETHOD_END,g in order to fully hide the explicit mention
of kobj(9) from device drivers.

Factor out the duplicated macro for the device type used in the
OFW device tree for PCI bridges and add a new one for PCI Express.
While at it, take advantage of the former for the rman(9) work-
around in jbusppm(4).

Take advantage of KOBJMETHOD_END.

Add drivers for the power management devices found on Fireplane/
Safari- and JBus-based machines. Currently the main purpose of
these drivers is debugging of the resource allocation on nexus(4)
and the register content of these devices though.