event/dlb2: improve enqueue efficiency

event/dlb2: improve enqueue efficiency

If user tried to send 64 events, it will take 64 credits. Enqueue API
only gets 32 credits each time. If it does not have sufficient credits,
it just fails and returns. Enqueue API does not retry. On next enqueue,
it will get 32 more and send will work. This results in alternate
enqueues failing.

Add check to make sure DLB2_MAX_ENQUEUE_DEPTH <=
both DLB2_SW_CREDIT_QUANTA_DEFAULT and DLB2_SW_CREDIT_BATCH_SZ.

Add enough retires in the driver to satisfy max enqueue depth credits
based on set quanta. Note the credit quanta size is different for each
port. Retry count = Max enqueue depth / credit quanta in driver before
returning no credit.

Fixes: 3a6d0c04e7fb ("event/dlb2: add port setup")
Cc: stable@dpdk.org
Signed-off-by: Timothy McDaniel <timothy.mcdaniel@intel.com>