OvmfPkg/LoongArchVirt: Clear the PGD series registers

Since the PGD series registers are in an unknown state when reset, some
simulators will hang when restarting if these registers are not cleared,
so they are cleared in this patch.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Chao Li <lichao@loongson.cn>

OvmfPkg/LoongArchVirt/Library/CpuMmuInitLib/CpuMmuInit.c

@@ -141,6 +141,12 @@ ConfigureMemoryManagementUnit (
     return EFI_UNSUPPORTED;
   }
 
+  //
+  // Clear PGD series registers.
+  //
+  CsrWrite (LOONGARCH_CSR_PGDL, 0x0);
+  CsrWrite (LOONGARCH_CSR_PGDH, 0x0);
+
   PageTable = 0;
   while (MemoryTable->NumberOfPages != 0) {
     DEBUG ((