This patch adds the ability to have restricted write access to some

This patch adds the ability to have restricted write access to some
of the structures on the capability list. Specifically, this patch adds
support for reading data through the Vital Product Data capability
structure and for manipulating power management of a card. A driver
domain is not allowed to enable Power Management Events (the PME trace
may be shared across devices in many domains), but it can put a device
in its control to sleep or query it for power usage statistics. This
code could possibly be expanded in the future to add support for AGP,
PCI-X, and MSI/MSIX (all of which are controlled through structures on
the capability list).

This patch also corrects some formatting issues in the PCI backend and
adds some comments to the code regarding permissive mode.

Signed-off-by: Ryan Wilson <hap9@epoch.ncsc.mil>