net/bnxt: support flow API item parsing

net/bnxt: support flow API item parsing

1. Registers a callback handler for each rte_flow_item type, if it
   is supported
2. Iterates through each rte_flow_item till RTE_FLOW_ITEM_TYPE_END
3. Invokes the header call back handler
4. Each header call back handler will populate the respective fields
   in hdr_field & hdr_bitmap

Signed-off-by: Kishore Padmanabha <kishore.padmanabha@broadcom.com>
Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>