netifd/config.sh: remove some bashism (usage of [[)

"[[" is a bash extension for test. As the ash-implementation is not
fully compatible we drop its usage.

Signed-off-by: Sven Roederer <devel-sven@geroedel.de>

package/network/config/netifd/files/lib/network/config.sh

@@ -12,7 +12,7 @@ find_config() {
 			json_load "$(ifstatus $interface)"
 			json_get_var ifdev device
 			json_get_var ifl3dev l3_device
-			if [[ "$device" = "$ifdev" ]] || [[ "$device" = "$ifl3dev" ]]; then
+			if [ "$device" = "$ifdev" ] || [ "$device" = "$ifl3dev" ]; then
 				echo "$interface"
 				exit 0
 			else