MdePkg ACPI: Correct processor struct of PPTT
    
    The Type field of EFI_ACPI_6_2_PPTT_STRUCTURE_PROCESSOR should
    be UINT8 as ACPI version 6.2 specification.
    
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed-off-by: Ming Huang <huangming23@huawei.com>
    Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
    Reviewed-by: Star Zeng <star.zeng@intel.com>
    Reviewed-by: Liming Gao <liming.gao@intel.com>