regmap: permit to set reg_update_bits with bulk implementation

A regmap may still require to set a custom reg_update_bits instead of
relying to the regmap_bus_read/write general function.

Permit to set it in the map if provided by the regmap config.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20220715201032.19507-1-ansuelsmth@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regmap.c

@@ -882,6 +882,8 @@ struct regmap *__regmap_init(struct device *dev,
 
 	if (config && config->read && config->write) {
 		map->reg_read  = _regmap_bus_read;
+		if (config->reg_update_bits)
+			map->reg_update_bits = config->reg_update_bits;
 
 		/* Bulk read/write */
 		map->read = config->read;