rtc: mc146818-lib: refactor mc146818_does_rtc_work

Refactor mc146818_does_rtc_work() so that it uses mc146818_avoid_UIP().
It is enough to call mc146818_avoid_UIP() with no callback.

Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211210200131.153887-8-mat.jonczyk@o2.pl