doc: Kernel event logger documentation

Add the kernel event logger documentation where the user can find
how to use this mechanism and which event logging points are
available currently.

Change-Id: I6d86c7b79c6b4a56a9e3514b6c4933a35e0c782f
Signed-off-by: Yonattan Louise <yonattan.a.louise.mendoza@intel.com>