MdePkg/Include/IndustryStandard: CXL 1.1 Registers

MdePkg/Include/IndustryStandard: CXL 1.1 Registers

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2611

Register definitions from chapter 7 of Compute Express Link
Specification Revision 1.1 are ported into the new Cxl11.h.
The CXL Flex Bus registers are based on the PCIe Extended Capability
DVSEC structure header, led to the inclusion of upgraded Pci.h.

Signed-off-by: Ashraf Javeed <ashraf.javeed@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>