OvmfPkg/PlatformDxe: Check RouteConfig arguments for spec compliance
Per UEFI Spec 2.9, EFI_HII_CONFIG_ROUTING_PROTOCOL.RouteConfig()
should return EFI_INVALID_PARAMETER if caller passes in a NULL for
the Configuration parameter (see 35.4 EFI HII Configuration Routing
Protocol).
Add a check to return EFI_INVALID_PARAMETER when Configuration is NULL.