opkg: use $(PROJECT_GIT), $(AUTORELEASE) and SPDX

1) Use SPDX license headers to be machine readable.
2) Update copyright to 2021.
3) Use $(PROJECT_GIT) instead of manually specifying the git url.
4) Use $(AUTORELEASE) to automatically set the correct PKG_RELEASE.

Signed-off-by: Nick Hainke <[email protected]>

package/system/opkg/Makefile

@@ -1,19 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
 #
-# Copyright (C) 2006-2015 OpenWrt.org
-# Copyright (C) 2016-2017 LEDE Project
+# Copyright (C) 2006-2021 OpenWrt.org
 #
-# This is free software, licensed under the GNU General Public License v2.
-# See /LICENSE for more information.
 
 include $(TOPDIR)/rules.mk
 include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=opkg
-PKG_RELEASE:=1
+PKG_RELEASE:=$(AUTORELEASE)
 PKG_FLAGS:=essential
 
 PKG_SOURCE_PROTO:=git
-PKG_SOURCE_URL:=https://git.openwrt.org/project/opkg-lede.git
+PKG_SOURCE_URL:=$(PROJECT_GIT)/project/opkg-lede.git
 PKG_SOURCE_DATE:=2021-03-15
 PKG_SOURCE_VERSION:=5936c4f9660248284e8a9b040ea3153d3ea888de
 PKG_MIRROR_HASH:=b873c209baaf4f150c89646d58e4a0072f807d24b02c320ab8c7ae9180c13240