fan-ctrl: use .c file as license file

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/fan-ctrl/fan-ctrl.mk

@@ -9,6 +9,7 @@ FAN_CTRL_VERSION = 1.3
 FAN_CTRL_SOURCE = fan-ctrl.c?revision=$(FAN_CTRL_VERSION)
 FAN_CTRL_SITE = http://fan-ctrl.cvs.sourceforge.net/viewvc/fan-ctrl/fan-ctrl/
 FAN_CTRL_LICENSE = GPLv2+
+FAN_CTRL_LICENSE_FILES = fan-ctrl.c
 
 define FAN_CTRL_EXTRACT_CMDS
 	cp $(DL_DIR)/$(FAN_CTRL_SOURCE) $(@D)/fan-ctrl.c