package/linux-headers: add licensing information

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Luca Ceresoli <luca@lucaceresoli.net>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/linux-headers/linux-headers.mk

@@ -16,6 +16,8 @@ else ifeq ($(findstring x4.,x$(LINUX_HEADERS_VERSION)),x4.)
 LINUX_HEADERS_SITE = $(BR2_KERNEL_MIRROR)/linux/kernel/v4.x
 endif
 LINUX_HEADERS_SOURCE = linux-$(LINUX_HEADERS_VERSION).tar.xz
+LINUX_HEADERS_LICENSE = GPLv2
+LINUX_HEADERS_LICENSE_FILES = COPYING
 
 LINUX_HEADERS_INSTALL_STAGING = YES