staging: iio: resolver: ad2s1210: simplify code with guard(mutex)

We can simplify the code and get rid of most of the gotos by using
guard(mutex) from cleanup.h.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231010-ad2s1210-mainline-v5-3-35a0f6ffa04a@baylibre.com


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