watchdog: mlx-wdt: Use regmap_write_bits()

Use the regmap_write_bits() macro instead of regmap_update_bits_base().
No functional change.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210907092732.31815-1-p.zabel@pengutronix.de


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>