rtc: s5m: replace regmap_update_bits with regmap_clear/set_bits

The regmap_clear_bits() and regmap_set_bits() helper macros state the
intention a bit more obviously.

Use those.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20250409-s2mpg10-v4-30-d66d5f39b6bf@linaro.org


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