doc: add notes about eventdev producer/consumer dependency

doc: add notes about eventdev producer/consumer dependency

EventDev i.e consumer needs to be started before starting the
event producers.
Update documentation of EventDev and EventDev adapters.

Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
Reviewed-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
Reviewed-by: Abhinandan Gujjar <abhinandan.gujjar@intel.com>