patch: add PKG_LICENSE information.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>

devel/patch/Makefile

@@ -14,6 +14,8 @@ PKG_RELEASE:=1
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=@GNU/patch
 PKG_MD5SUM:=95dd8d7e41dcbcecdd5cd88ef915378d
+PKG_LICENSE:=GPL-3.0+
+PKG_LICENSE_FILES:=COPYING
 
 include $(INCLUDE_DIR)/package.mk