nlbwmon: preserve protocols mapping across sysupgrade

Define package config files to preserve
/usr/share/nlbwmon/protocols across sysupgrade

Signed-off-by: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>

net/nlbwmon/Makefile

@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=nlbwmon
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/jow-/nlbwmon.git
@@ -39,4 +39,9 @@ define Package/nlbwmon/install
 	$(INSTALL_CONF) ./files/nlbwmon.config $(1)/etc/config/nlbwmon
 endef
 
+define Package/nlbwmon/conffiles
+/usr/share/nlbwmon/protocols
+endef
+
+
 $(eval $(call BuildPackage,nlbwmon))