IntelSiliconPkg/IgdOpRegion: Add definition for Intel IGD

IntelSiliconPkg/IgdOpRegion: Add definition for Intel IGD
 OpRegion.

Add IGD OpRegion definition from Intel Integrated Graphics Device OpRegion
Specification.
at https://01.org/sites/default/files/documentation/acpi_igd_opregion_spec_0.pdf

Previous submission seems appears to be cut off. I do not know why.
Add missing part here.

Cc: Giri P Mudusuru <giri.p.mudusuru@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Giri P Mudusuru <giri.p.mudusuru@intel.com>