[PATCH 0 of 4 v2] Add commands to automatically prep devices for pass-through

[George Dunlap <george.dunlap@eu.citrix.com>]

Add commands to automatically prep devices for pass-through

The current method for passing through devices requires users to
either modify cryptic Linux boot parameters and reboot, or do a lot of
manual reads and writes into sysfs nodes.

This set of patches introduces commands to make this easier.  It expands
on the concept of "assignable" (from the list_assignable_devices command).

The new xl commands are:

pci_assignable_add: Make a device assignable to guests.  This involves
unbinding the device from its old driver, creating a slot for it in
pciback (if necessary), and binding it to pciback.

pci_assignable_list: List devices assignable to guests.  Just renamed
from pci_list_assignable.

pci_assignable_remove: Make the device no longer assignable to guests. 
This involves unbinding the device from pciback and removing the slot.  It 
optionally involves rebinding the device to the driver from which we stole
it.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>