examples/eventdev: add info output for main core

examples/eventdev: add info output for main core

When the main core is set as tx/rx/sched/worker core, it also needs to
print some information to show this. Thus, add info output for the main
core, and add a "dump" function to print core information for the sake
of code simplicity and easy maintenance.

In the meanwhile, fix the count error. For the variable "worker_idx", it
should be incremented when the core is set as worker core. However, when
the main core is set as rx/tx/sched core, the worker_idx is also
incremented. Though this error may not have a substantial impact due to
that the main core is the last launched core, but it should be corrected
from the perspective of code correctness.

Fixes: 1094ca96689c ("doc: add SW eventdev pipeline to sample app guide")
Cc: stable@dpdk.org
Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>