iio: adc: stm32-dfsdm: drop __func__ while using Dynamic debug

Dropped __func__ while using dev_dbg() and pr_debug()
If the function name is desired, it can be configured using
dynamic debug.

Signed-off-by: Mugilraj Dhavachelvan <dmugil2000@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210401154343.41527-1-dmugil2000@gmail.com


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