Fix the following warning:
drivers/rtc/rtc-v3020.c: In function ‘rtc_probe’:
drivers/rtc/rtc-v3020.c:287:6: warning: variable ‘temp’ set but not used [-Wunused-but-set-variable]

Link: https://lore.kernel.org/r/20191122102212.400158-9-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>