rtc: ds1343: use regmap_update_bits for glitch filter

Use regmap_update_bits to update DS1343_CONTROL_REG in a race free manner
when setting the glitch filter.

Link: https://lore.kernel.org/r/20191019204941.6203-5-alexandre.belloni@bootlin.com


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