mac80211: simplify TDLS RA lookup

smatch pointed out that the second check of "tdls_auth" was
pointless since if it was true, we returned from the function
already. We can further simplify the code by moving the first
check (if it's a TDLS peer at all) into the outer if, to only
handle that inside. This simplifies the control flow here.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>