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/docs/getting_started/porting-guide.rst b/docs/getting_started/porting-guide.rst
index f331616..19e26e4 100644
--- a/docs/getting_started/porting-guide.rst
+++ b/docs/getting_started/porting-guide.rst
@@ -2724,12 +2724,11 @@
 ::
 
     Argument : void
-    Return   : int
+    Return   : void
 
 This API is used by the crash reporting mechanism to force write of all buffered
 data on the designated crash console. It should only use general purpose
-registers x0 through x5 to do its work. The return value is 0 on successful
-completion; otherwise the return value is -1.
+registers x0 through x5 to do its work.
 
 .. _External Abort handling and RAS Support: