wifi: cfg80211: drop BSS elements from assoc trace for now

For multi-link operation, this cannot work as the req->bss pointer
will be NULL, and we'll need to do more work on this to really add
tracing for the MLO case here. Drop the BSS elements for now as
they're not the most useful thing, and it's hard to size things
correctly for the MLO case (without adding a lot of code that's
also executed when tracing isn't enabled.)

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>