grub: add license information

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

boot/grub/grub.mk

@@ -9,6 +9,9 @@ GRUB_SOURCE = grub_$(GRUB_VERSION).orig.tar.gz
 GRUB_PATCH  = grub_$(GRUB_VERSION)-35.diff.gz
 GRUB_SITE   = http://snapshot.debian.org/archive/debian/20080329T000000Z/pool/main/g/grub/
 
+GRUB_LICENSE = GPLv2+
+GRUB_LICENSE_FILES = COPYING
+
 GRUB_CFLAGS=-DSUPPORT_LOOPDEV
 ifeq ($(BR2_LARGEFILE),)
 GRUB_CFLAGS+=-U_FILE_OFFSET_BITS