rtc: pcf85063: Add a compatible entry for pca85073a

The PCA85073A RTC has the same programming model as the PCF85063A.

Add a compatible entry for it.

Tested on a custom i.MX6SX based board.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220419014445.341444-2-festevam@gmail.com