libexif: Add PKG_LICENSE information.

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

libs/libexif/Makefile

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2006-2010 OpenWrt.org
+# Copyright (C) 2006-2014 OpenWrt.org
 #
 # This is free software, licensed under the GNU General Public License v2.
 # See /LICENSE for more information.
@@ -15,6 +15,9 @@ PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL:=@SF/libexif
 PKG_MD5SUM:=27339b89850f28c8f1c237f233e05b27
 
+PKG_LICENSE:=LGPL-2.1
+PKG_LICENSE_FILES:=COPYING
+
 PKG_FIXUP:=autoreconf
 PKG_INSTALL:=1