macchanger: add license file

[Peter: use the "main" source file, main.c]
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/macchanger/macchanger.mk

@@ -7,5 +7,6 @@
 MACCHANGER_VERSION = 1.6.0
 MACCHANGER_SITE = $(BR2_GNU_MIRROR)/macchanger
 MACCHANGER_LICENSE = GPLv2+
+MACCHANGER_LICENSE_FILES = src/main.c
 
 $(eval $(autotools-package))