OvmfPkg/VirtioFsDxe: Check GetDriverName arguments

The current implementation does not check if Language or DriverName
are NULL. This causes the SCT test suite to crash.

Add a check to return EFI_INVALID_PARAMETER if any of these pointers
are NULL.

Signed-off-by: Dimitrije Pavlov <Dimitrije.Pavlov@arm.com>
Reviewed-by: Sunny Wang <sunny.wang@arm.com>

OvmfPkg/VirtioFsDxe/DriverBinding.c

@@ -218,6 +218,10 @@ VirtioFsGetDriverName (
   OUT CHAR16                        **DriverName
   )
 {
+  if ((Language == NULL) || (DriverName == NULL)) {
+    return EFI_INVALID_PARAMETER;
+  }
+
   if (AsciiStrCmp (Language, "en") != 0) {
     return EFI_UNSUPPORTED;
   }