iio: accel: bmc150: Remove redundant __func__ in dev_dbg()

Dynamic debug has a run time knob to enable function name printing.
Remove this from dev_dbg() calls.

Furthermore, functional tracing when enabled can show what function is
called, therefore remove empty dev_dbg() calls.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>