test/event: remove eth Rx adapter vdev workaround

test/event: remove eth Rx adapter vdev workaround

eth Rx adapter has been updated to support hotplugged
devices, devices created after adapter creation can now be
added to the adapter.

Update the adapter_multi_eth_add_del
test case to create the adapter as part of test setup
instead of creating it after creating vdevs.

Fixes: 2a9c83ae3b2e ("test/eventdev: add multi-ports test")
Cc: stable@dpdk.org
Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>