iio: accel: bma220: Fix returned codes from bma220_init(), bma220_deinit()

Potentially bma220_init() and bma220_deinit() may return positive codes.
Fix the logic to return proper error codes instead.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200831090813.78841-1-andriy.shevchenko@linux.intel.com


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