Add CsrRead, CsrWrite and CsrXChg functions for LoongArch, and use them
to operate the CSR register of LoongArch architecture.
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4584
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Signed-off-by: Chao Li <lichao@loongson.cn>
Co-authored-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Chao Li