iio: resolver: ad2s1210: use bitmap_write

Replace bitmap array access with bitmap_write.

Accessing the bitmap array directly is not recommended and now there is
a helper function that can be used.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250210-gpio-set-array-helper-v3-10-d6a673674da8@baylibre.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>