arch: nds32: Kconfig: pedantic formatting

Formatting of Kconfig files doesn't look so pretty, so let the
Great White Handkerchief come around and clean it up.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>