sane-backends: add license information

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/sane-backends/sane-backends.mk

@@ -7,6 +7,8 @@
 SANE_BACKENDS_VERSION = 1.0.22
 SANE_BACKENDS_SITE = http://sources.buildroot.net/
 SANE_BACKENDS_CONFIG_SCRIPTS = sane-config
+SANE_BACKENDS_LICENSE = GPLv2+
+SANE_BACKENDS_LICENSE_FILES = COPYING
 
 ifeq ($(BR2_PACKAGE_LIBUSB),y)
 SANE_BACKENDS_DEPENDENCIES += libusb