orbit: fix ORBIT_LICENSE_FILES

Fixes:

  http://autobuild.buildroot.org/results/33e/33e4e65301679e46cd80a1a123f45647376e60ce/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/orbit/orbit.mk

@@ -7,7 +7,7 @@
 ORBIT_VERSION = 2.2.0
 ORBIT_SITE = http://github.com/downloads/keplerproject/orbit
 ORBIT_LICENSE = MIT
-ORBIT_LICENSE_FILES = COPYRIGHT
+ORBIT_LICENSE_FILES = doc/us/license.md
 
 define ORBIT_INSTALL_TARGET_CMDS
 	$(MAKE) -C $(@D) \