tracing/fastboot: fix printk format typo in boot tracer

When printing nanoseconds, the right printk format string is %09 not %06...

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Frédéric Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>