UefiCpuPkg: RISC-V: Support MMU with SV39/48/57 mode

During CpuDxe initialization, MMU will be setup with the highest
mode that HW supports.

Signed-off-by: Tuan Phan <tphan@ventanamicro.com>
Reviewed-by: Andrei Warkentin <andrei.warkentin@intel.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

UefiCpuPkg/CpuDxeRiscV64/CpuDxe.c

@@ -296,8 +296,7 @@ CpuSetMemoryAttributes (
   IN UINT64                 Attributes
   )
 {
-  DEBUG ((DEBUG_INFO, "%a: Set memory attributes not supported yet\n", __func__));
-  return EFI_SUCCESS;
+  return RiscVSetMemoryAttributes (BaseAddress, Length, Attributes);
 }
 
 /**
@@ -340,6 +339,12 @@ InitializeCpu (
   //
   DisableInterrupts ();
 
+  //
+  // Enable MMU
+  //
+  Status = RiscVConfigureMmu ();
+  ASSERT_EFI_ERROR (Status);
+
   //
   // Install Boot protocol
   //