bnge: return after auxiliary_device_uninit() in error path

In the Linux kernel, the following vulnerability has been resolved:

bnge: return after auxiliary_device_uninit() in error path

When auxiliary_device_add() fails, the error block calls
auxiliary_device_uninit() but does not return. The uninit drops the
last reference and synchronously runs bnge_aux_dev_release(), which sets
bd->auxr_dev = NULL and frees the underlying object. The subsequent
bd->auxr_dev->net = bd->netdev then dereferences NULL, which is not a
good thing to have happen when trying to clean up from an error.

Add the missing return, as the auxiliary bus documentation states is a
requirement (seems that LLM tools read documentation better than humans
do...)