Add and use plat_crash_console_flush() API

This API makes sure that all the characters sent to the crash console
are output before returning from it.

Porting guide updated.

Change-Id: I1785f970a40f6aacfbe592b6a911b1f249bb2735
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/bl31/aarch64/crash_reporting.S b/bl31/aarch64/crash_reporting.S
index 8e60386..c6d5c6c 100644
--- a/bl31/aarch64/crash_reporting.S
+++ b/bl31/aarch64/crash_reporting.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2017, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -349,6 +349,8 @@
 	/* Print some platform registers */
 	plat_crash_print_regs
 
+	bl	plat_crash_console_flush
+
 	/* Done reporting */
 	no_ret	plat_panic_handler
 endfunc do_crash_reporting