MdePkg: Add LoongArch Cpucfg function

Add LoongArch AsmCpucfg function and Cpucfg definitions.

Also added Include/Register/LoongArch64/Cpucfg.h to IgnoreFiles of
EccCheck.

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>
Acked-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

MdePkg/Library/BaseLib/BaseLib.inf

@@ -421,6 +421,7 @@
   LoongArch64/SetJumpLongJump.S     | GCC
   LoongArch64/SwitchStack.S         | GCC
   LoongArch64/ExceptionBase.S       | GCC
+  LoongArch64/Cpucfg.S              | GCC
 
 [Packages]
   MdePkg/MdePkg.dec