vfio/pci: Bypass IGD init in case of -ENODEV

[ Upstream commit e4eccb853664de7bcf9518fb658f35e748bf1f68 ]

Bypass the IGD initialization when -ENODEV returns,
that should be the case if opregion is not available for IGD
or within discrete graphics device's option ROM,
or host/lpc bridge is not found.

Then use of -ENODEV here means no special device resources found
which needs special care for VFIO, but we still allow other normal
device resource access.

Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Xiong Zhang <xiong.y.zhang@intel.com>
Cc: Hang Yuan <hang.yuan@linux.intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Fred Gao <fred.gao@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>