GUID value used for PcdTpmInstanceGuid to indicate TPM 1.2 device is selected to support.
Include/Guid/TpmInstance.h

GUID Information

GUID's Guid Name	GUID's Guid
gEfiTpmDeviceInstanceTpm12Guid	{ 0x8b01e5b6, 0x4f19, 0x46e8, { 0xab, 0x93, 0x1c, 0x53, 0x67, 0x1b, 0x90, 0xcc } }

Refer to Header File