Fixes warning from platsupport shodan uart_init

Only ps_cdev_init is lacking a default implementation, and there's a
trivial one in chardev.c in the same directory as this. It would be nice
if we could also delete that, but the lack of a non-plat definition
prevents that.

Change-Id: I31dd53688c2e534299437df9cd5af7f9486aa2ef

libplatsupport/src/plat/shodan/serial.c

diff --git a/libplatsupport/src/plat/shodan/serial.c b/libplatsupport/src/plat/shodan/serial.c
deleted file mode 100644
index aa2b0e7..0000000
--- a/libplatsupport/src/plat/shodan/serial.c
+++ /dev/null
@@ -1,23 +0,0 @@
-/*
- * Copyright 2018, Data61
- * Commonwealth Scientific and Industrial Research Organisation (CSIRO)
- * ABN 41 687 119 230.
- *
- * This software may be distributed and modified according to the terms of
- * the BSD 2-Clause license. Note that NO WARRANTY is provided.
- * See "LICENSE_BSD2.txt" for details.
- *
- * @TAG(DATA61_BSD)
- */
-#include <stdlib.h>
-#include <platsupport/serial.h>
-#include <platsupport/plat/serial.h>
-#include <string.h>
-
-
-int uart_init(const struct dev_defn* defn,
-              const ps_io_ops_t* ops,
-              ps_chardevice_t* dev)
-{
-    return 0;
-}