Don't return error information from console_flush

And from crash_console_flush.

We ignore the error information return by console_flush in _every_
place where we call it, and casting the return type to void does not
work around the MISRA violation that this causes. Instead, we collect
the error information from the driver (to avoid changing that API), and
don't return it to the caller.

Change-Id: I1e35afe01764d5c8f0efd04f8949d333ffb688c1
Signed-off-by: Jimmy Brisson <jimmy.brisson@arm.com>
diff --git a/plat/imx/common/lpuart_console.S b/plat/imx/common/lpuart_console.S
index 98b3588..ff01e35 100644
--- a/plat/imx/common/lpuart_console.S
+++ b/plat/imx/common/lpuart_console.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -72,6 +72,5 @@
 endfunc console_lpuart_getc
 
 func console_lpuart_flush
-	mov	x0, #0
 	ret
 endfunc console_lpuart_flush