make shell math operations style more succulent

Convert the style:
	var=$((${var} + 1))
to:
	: $(( var += 1 ))

The latter is easier to read imo.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

net/wpa_supplicant.sh

@@ -34,7 +34,7 @@ _get_ssid()
 			return 0
 		fi
 		sleep 1
-		timeout=$((timeout - 1))
+		: $(( timeout -= 1 ))
 	done
 
 	return 1