[PATCH 2/2] qemu: Support MULTI_CONSOLE_API

Add support for the new MULTI_CONSOLE_API

Crash information is now displayed in both the runtime and crash consoles,
if a crash occurs after the runtime console has been enabled

Enable MULTI_CONSOLE_API by default on qemu builds

Fixes ARM-software/tf-issues#561

Signed-off-by: Michalis Pappas <mpappas@fastmail.fm>