rtc: pcf2127: fix error code in pcf2127_enable_ts()

This error path accidentally returns success.  Return -EINVAL instead.

Fixes: 420cc9e8 ("rtc: pcf2127: add support for multiple TS functions")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Reviewed-by: Hugo Villeneuve <hugo@hugovil.com>
Reviewed-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/55b9c84b-9d21-444f-b91a-cf9316b65833@moroto.mountain


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>