procd: allow optional watchdog instance parameter

Optional instance watchdog timeout and watchdog mode can be set by
adding: procd_set_param $mode $timeout

$mode is an integer [0-1] representing instance watchdog mode of
operation:
0 = disabled
1 = passive mode, client must periodically poke watchdog via ubus

$timeout is an integer representing how often, in seconds, the watchdog must be poked.

Signed-off-by: Daniel Bailey <danielb@meshplusplus.com>

package/system/procd/files/procd.sh

@@ -247,7 +247,7 @@ _procd_set_param() {
 		env|data|limits)
 			_procd_add_table "$type" "$@"
 		;;
-		command|netdev|file|respawn|watch)
+		command|netdev|file|respawn|watch|watchdog)
 			_procd_add_array "$type" "$@"
 		;;
 		error)
@@ -378,7 +378,7 @@ _procd_append_param() {
 		env|data|limits)
 			_procd_add_table_data "$@"
 		;;
-		command|netdev|file|respawn|watch)
+		command|netdev|file|respawn|watch|watchdog)
 			_procd_add_array_data "$@"
 		;;
 		error)