event/dlb2: optimize credit allocations using port

event/dlb2: optimize credit allocations using port

This commit implements the changes required for using suggested
port type hint feature. Each port uses different credit quanta
based on port type specified using port configuration flags.

Each port has separate quanta defined in dlb2_priv.h
Producer and consumer ports will need larger quanta value to reduce number
of credit calls they make. Workers can use small quanta as they mostly
work out of locally cached credits and don't request/return credits often.

Signed-off-by: Pravin Pathak <pravin.pathak@intel.com>