passthrough: hot-plug PCI devices at boot-time

passthrough: hot-plug PCI devices at boot-time

Currently there are two interfaces to pass-through PCI devices:
1. A method driven through per-device xenstore entries that is used at boot-time
2. An event-based method used for hot-plug.

This seems somewhat redundant and makes extending the code cumbersome
and prone to error - often the change needs to be made twice, in
two different ways.

This patch removes support for the boot-time protocol from qemu-xen.

There is a companion patch for xend which uses the hot-plug protocol
at boot time.

Cc: Edwin Zhai <edwin.zhai@intel.com>
Cc: Masaki Kanno <kanno.masaki@jp.fujitsu.com>
Signed-off-by: Simon Horman <horms@verge.net.au>