iio: adc: ti-ads124s08: Switch to fsleep()

iio: adc: ti-ads124s08: Switch to fsleep()

According to Documentation/timers/delay_sleep_functions.rst,
fsleep() is the preferred delay function to be used in non-atomic
context, so switch to it accordingly.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Fabio Estevam <festevam@denx.de>
Link: https://patch.msgid.link/20241209181624.1260868-1-festevam@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>