iwmc3200wifi: add ftrace event tracing support

Add event tracer for iwmc3200wifi driver. When enabled, all the
commands and responses between the driver and firmware (also
including Tx/Rx frames) will be recorded in the ftrace ring buffer.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>