base-files: Changed UCI variable name for GPIO value from 'default' to 'value'

This changes the UCI variable for the GPIO value from system.$cfg.default back
to system.$cfg.value as it was before the change from uci-defaults [1] to board.d.
/etc/init.d/gpio_switch [2] still expects the value to be in system.$cfg.value.

[1] d65916047b/package/base-files/files/lib/functions/uci-defaults.sh (L197)
[2] https://github.com/lede-project/source/blob/master/package/base-files/files/etc/init.d/gpio_switch#L17

Signed-off-by: Julian Labus <julian@labus-online.de>

package/base-files/files/bin/config_generate

@@ -401,7 +401,7 @@ generate_gpioswitch() {
 				set system.$cfg='gpio_switch'
 				set system.$cfg.name='$name'
 				set system.$cfg.gpio_pin='$pin'
-				set system.$cfg.default='$default'
+				set system.$cfg.value='$default'
 			EOF
 		json_select ..
 	json_select ..