staging: greybus: Remove duplicate include file

This patch removed duplicated include line.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/authentication.c

@@ -16,7 +16,6 @@
 
 #include "greybus_authentication.h"
 #include "firmware.h"
-#include "greybus.h"
 
 #define CAP_TIMEOUT_MS		1000