rtc: rx8010: use a helper variable for client->dev in probe()

Simple 'dev' looks better then repeated &client->dev and has the added
benefit of avoiding unnecessary line breaks.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-10-brgl@bgdev.pl