drm/i915/gvt: Add support for opregion virtualization

opregion emulated with a copy from host which leads to some display
bugs such as guest resolution adjustment failure due to host opregion
fail to claim port D support. with a fake opregion table provided
to fully emulate opregion to meet guest port requirement.

v1 - initial patch
v2 - reforamt opregion arrary with 0x02x output
v3 - opregion array removed with opregion generation on host initizaiton
v4 - rebased v3 patch from stable branch to staging branch which also has
     different struct child_device_config and addressed v3 review comments.

Signed-off-by: Xiaolin Zhang <xiaolin.zhang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>