drivers/ieee802154_kw41z: Update kw41z to support event trace buffer

Added conditionally enabled event state tracing support.
Needed for enhanced debug visibility of tight timed events where
normal print debug messages affect the timing of things. This is a
simple buffer that allows post analysis via gdb of what sequencer
events occurred.

Signed-off-by: David Leach <david.leach@nxp.com>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>