MdePkg/Include: LoongArch definitions.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4053

Add LoongArch processor related definitions.

For the Http boot and PXE boot types seeing this URL section "Processor
Architecture Type" for the LOONGARCH values:
https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml

For definitions of PE/COFF and LOONGARCH relocation types, see the
"Machine Types" and "Basic Relocation Types" sections of this URL for
LOONGARCH values:
https://docs.microsoft.com/en-us/windows/win32/debug/pe-format

For the register definitions of exceptions context, see the UEFI V2.10
18.2.2, 18.2.4 and 18.2.5 sections of this URL for LOONGARCH
definitions:
https://uefi.org/specs/UEFI/2.10/18_Protocols_Debugger_Support.html

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

MdePkg/Include/Protocol/PxeBaseCode.h

@@ -4,6 +4,7 @@
 
 Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
 Copyright (c) 2020, Hewlett Packard Enterprise Development LP. All rights reserved.<BR>
+Copyright (c) 2022, Loongson Technology Corporation Limited. All rights reserved.<BR>
 
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -158,6 +159,8 @@ typedef UINT16 EFI_PXE_BASE_CODE_UDP_PORT;
 #define EFI_PXE_CLIENT_SYSTEM_ARCHITECTURE  0x000B
 #elif defined (MDE_CPU_RISCV64)
 #define EFI_PXE_CLIENT_SYSTEM_ARCHITECTURE  0x001B
+#elif defined (MDE_CPU_LOONGARCH64)
+#define EFI_PXE_CLIENT_SYSTEM_ARCHITECTURE  0x0027
 #endif
 
 ///