diffutils: update license

Signed-off-by: Qing He <qing.he@intel.com>

meta/recipes-extended/diffutils/diffutils_2.8.1.bb

@@ -1,8 +1,10 @@
-SECTION = "base"
-LICENSE = "GPL"
 DESCRIPTION = "Diffutils contains the GNU diff, diff3, \
 sdiff, and cmp utilities. These programs are usually \
 used for creating patch files."
+SECTION = "base"
+LICENSE = "GPLv2+"
+LIC_FILES_CHKSUM = "file://COPYING;md5=94d55d512a9ba36caa9b7df079bae19f"
+
 PR = "r4"
 
 SRC_URI = "${GNU_MIRROR}/diffutils/diffutils-${PV}.tar.gz"