tracing: Split tracing initialization into two for early initialization

tracing: Split tracing initialization into two for early initialization

Create an early_trace_init() function that will initialize the buffers and
allow for ealier use of trace_printk(). This will also allow for future work
to have function tracing start earlier at boot up.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>