mac80211_hwsim: fix check for custom world regdom array size

David Binderman reports that the conditions in the first loop
are the wrong way around - checking the array contents before
the size.

Instead of leaving the empty loop there and reordering the two
checks unify it into a single loop that skips over non-matches
and exits after the first match.

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>