passthrough: graphics passthrough cleanup

passthrough: graphics passthrough cleanup

This patch as originally titled Calpella/Sandybridge IGD passthrough.
In this revision, I have separated cleanup portion of the patch from
Calpella/Sandybridge portion.  This cleanup portion incorporates
inputs from Stephano and proposed patch from Isaku.  The main changes
are consolidating graphics passthrough specific code into
pt-graphics.c and removal of hardcoded intercepts for host bridge
(device 00:00.0) accesses in pci.c.

Signed-off-by: Allen Kay [allen.m.kay@intel.com<mailto:allen.m.kay@intel.com>]
Signed-off-by: Isaku Yamahata [yamahata@valinux.co.jp]