driver core: auxiliary bus: Fix IS_ERR() vs NULL mixup in __devm_auxiliary_device_create()

This code was originally going to use error pointers but we decided it
should return NULL instead.  The error pointer code in
__devm_auxiliary_device_create() was left over from the first version.
Update it to use NULL.  No callers have been merged yet, so that makes
this change simple and self contained.

Fixes: eaa0d302 ("driver core: auxiliary bus: add device creation helpers")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Leon Romanovsky <leon@kernel.org>
Link: https://lore.kernel.org/r/aAi7Kg3aTguFD0fU@stanley.mountain


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>