pinctrl: mcp23s08: Kconfig: update to reflect supported features

Commit d8f4494e removed comments which described this limitation.
The code supported interrupts even before.

Also add some spacing so that the chip IDs are a bit more readable.

Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz>
Reviewed-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>