UefiCpuPkg: Add RISCV_EFI_BOOT_PROTOCOL related definitions

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4076

RISC-V UEFI based platforms need to support RISCV_EFI_BOOT_PROTOCOL.
Add this protocol GUID definition and the header file required.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Daniel Schaefer <git@danielschaefer.me>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Acked-by: Abner Chang <abner.chang@amd.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Andrei Warkentin <andrei.warkentin@intel.com>
Acked-by: Ray Ni <ray.ni@intel.com>

UefiCpuPkg/UefiCpuPkg.dec

@@ -86,6 +86,13 @@
   ## Include/Protocol/SmMonitorInit.h
   gEfiSmMonitorInitProtocolGuid  = { 0x228f344d, 0xb3de, 0x43bb, { 0xa4, 0xd7, 0xea, 0x20, 0xb, 0x1b, 0x14, 0x82 }}
 
+[Protocols.RISCV64]
+  #
+  # Protocols defined for RISC-V systems
+  #
+  ## Include/Protocol/RiscVBootProtocol.h
+  gRiscVEfiBootProtocolGuid  = { 0xccd15fec, 0x6f73, 0x4eec, { 0x83, 0x95, 0x3e, 0x69, 0xe4, 0xb9, 0x40, 0xbf }}
+
 #
 # [Error.gUefiCpuPkgTokenSpaceGuid]
 #   0x80000001 | Invalid value provided.