console: Fix console_unregister() signature

console_unregister() has always returned a pointer to the console that
was removed on success, not just an integer. Fix the C prototype to
match the assembly implementation.

Change-Id: Iafc43de0767a5c87c9ae5c3aba53761dd28d51e6
Signed-off-by: Julius Werner <jwerner@chromium.org>

include/drivers/console.h

@@ -52,8 +52,9 @@ typedef struct console {
  * implementation, e.g. console_16550_register() from <uart_16550.h>. Consoles
  * registered that way can be unregistered/reconfigured with below functions.
  */
-/* Remove a single console_t instance from the console list. */
-int console_unregister(console_t *console);
+/* Remove a single console_t instance from the console list. Return a pointer to
+ * the console that was removed if it was found, or NULL if not. */
+console_t *console_unregister(console_t *console);
 /* Returns 1 if this console is already registered, 0 if not */
 int console_is_registered(console_t *console);
 /*