greybus: get rid of a compile warning

The compiler has no way of knowing whether a called function will
actually assign something to the object whose address is passed as
an argument.  So it must assume it won't happen, and this leads to a
compile warning.  Fix this.
Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/es2.c

@@ -611,7 +611,7 @@ static int cport_reset(struct gb_host_device *hd, u16 cport_id)
 	struct usb_device *udev = es2->usb_dev;
 	struct arpc_cport_reset req;
 	int retval;
-	int result;
+	int result = 0;
 
 	switch (cport_id) {
 	case GB_SVC_CPORT_ID: