rtc: pcf2127: properly set flag WD_CD for rtc chips(pcf2129, pca2129)

Properly set flag WD_CD for rtc chips(pcf2129, pca2129)

Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201202031840.15582-1-biwen.li@oss.nxp.com