rtc: pcf2127: convert to devm_rtc_allocate_device

This allows further improvement of the driver.

Signed-off-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Link: https://lore.kernel.org/r/20190822131936.18772-1-bruno.thomsen@gmail.com


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