syslinux: add license information

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

boot/syslinux/syslinux.mk

@@ -8,6 +8,9 @@ SYSLINUX_VERSION = 4.05
 SYSLINUX_SOURCE  = syslinux-$(SYSLINUX_VERSION).tar.bz2
 SYSLINUX_SITE    = $(BR2_KERNEL_MIRROR)/linux/utils/boot/syslinux/4.xx/
 
+SYSLINUX_LICENSE = GPLv2+
+SYSLINUX_LICENSE_FILES = COPYING
+
 SYSLINUX_INSTALL_TARGET = NO
 SYSLINUX_INSTALL_IMAGES = YES