kea: fix kea-admin dependency

Fix kea-admin dependency where if procps-ng-ps wasn't available busybox 
would output an error casuse it does't support showing a processe's PID

Signed-off-by: Tiago Gaspar <tiagogaspar8@gmail.com>

net/kea/Makefile

@@ -70,7 +70,7 @@ endef
 define Package/kea-ctrl
 	$(call Package/kea/Default)
 	TITLE+=Control
-	DEPENDS:=+kea-dhcp4 \
+	DEPENDS:=+procps-ng +procps-ng-ps +kea-dhcp4 \
 	+IPV6:kea-dhcp6 +kea-dhcp-ddns
 endef
 define Package/kea-ctrl/description