iio: accel: msa311: Use correct header(s) instead of string_helpers.h

There is nothing from string_helpers.h used in the driver, correct
the header inclusion block accordingly.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Link: https://lore.kernel.org/r/20230808164152.66748-1-andriy.shevchenko@linux.intel.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/msa311.c

@@ -33,7 +33,7 @@
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
-#include <linux/string_helpers.h>
+#include <linux/string_choices.h>
 #include <linux/units.h>
 
 #include <linux/iio/buffer.h>