greybus: loopback: fix the type attribute check

In gb_loopback_check_attr(), the value of gb->type is checked for
validity.  The only valid values are 0, 1, and 2.  But the check
allows the value 3.  Fix that.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/loopback.c

@@ -123,7 +123,7 @@ static void gb_loopback_check_attr(struct gb_loopback *gb)
 {
 	if (gb->ms_wait > 1000)
 		gb->ms_wait = 1000;
-	if (gb->type > 3)
+	if (gb->type > 2)
 		gb->type = 0;
 	if (gb->size > GB_LOOPBACK_SIZE_MAX)
 		gb->size = GB_LOOPBACK_SIZE_MAX;