rtc: stm32: fix unnecessary parentheses

Fix a few style issues reported by checkpatch.pl:
- Unnecessary parentheses
- Lines should not end with a '('

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20230705174357.353616-8-valentin.caron@foss.st.com


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