dbus-triggerd: add license file

In absence of license file, use source file as a license file since it
has license header in comments.

Signed-off-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/dbus-triggerd/dbus-triggerd.mk

@@ -7,6 +7,7 @@
 DBUS_TRIGGERD_VERSION = ba3dbec805cb707c94c54de21666bf18b79bcc09
 DBUS_TRIGGERD_SITE = git://rg42.org/dbustriggerd.git
 DBUS_TRIGGERD_LICENSE = GPLv2+
+DBUS_TRIGGERD_LICENSE_FILES = dbus-triggerd.c
 DBUS_TRIGGERD_DEPENDENCIES = host-pkgconf dbus
 
 define DBUS_TRIGGERD_BUILD_CMDS