OvmfPkg/VirtioFsDxe: handle attribute updates in EFI_FILE_PROTOCOL.SetInfo
    
    Using the functions introduced previously, we can now update file
    attributes in VirtioFsSimpleFileSetInfo().
    
    Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
    Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>