rtc: pcf2123: rename struct and variables

Rename struct pcf2123_plat_data to struct pcf2123_data and pdata to
pcf2123 to make the driver use a more common subsystem style.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20190819182656.29744-5-alexandre.belloni@bootlin.com


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