rtc: pcf2127: add support for multiple TS functions

This will simplify the implementation of new variants into this driver.
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20230622145800.2442116-11-hugo@hugovil.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>