Add default crash console code to hook up to new console API

Add default crash console code to hook up to new console API

This patch expands the weak stubs for the plat_crash_console_xxx
functions in common platform code to use the new console API for crash
output. This should make crash console output "just work" for most cases
without the need for the platform to explicitly set up a crash console.
For cases where the normal console framework doesn't work (e.g. very
early crashes, before the platform can register any consoles), platforms
are still able to override the functions just like before.

This feature requires the MULTI_CONSOLE_API compile-time flag to work.
For builds which don't have it set, this patch has no practical effect.

Change-Id: I80dd161cb43f9db59a0bad2dae33c6560cfac584
Signed-off-by: Julius Werner <jwerner@chromium.org>