regmap: irq: Only update mask bits when doing initial mask

Don't write the full register, it's possible there's bits other than the
masks in the same register which we shouldn't be changing.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>

drivers/base/regmap/regmap-irq.c

@@ -306,7 +306,8 @@ int regmap_add_irq_chip(struct regmap *map, int irq, int irq_flags,
 		d->mask_buf[i] = d->mask_buf_def[i];
 		reg = chip->mask_base +
 			(i * map->reg_stride * d->irq_reg_stride);
-		ret = regmap_write(map, reg, d->mask_buf[i]);
+		ret = regmap_update_bits(map, reg,
+					 d->mask_buf[i], d->mask_buf[i]);
 		if (ret != 0) {
 			dev_err(map->dev, "Failed to set masks in 0x%x: %d\n",
 				reg, ret);