bnxt_en: Add new BNXT_FLTR_INSERTED flag to bnxt_filter_base struct.

Change the unused flag to BNXT_FLTR_INSERTED.  To prepare for multiple
pathways that an ntuple filter can be deleted, we add this flag.  These
filter structures can be retreived from the RCU hash table but only
the caller that sees that the BNXT_FLTR_INSERTED flag is set can delete
the filter structure and clear the flag under spinlock.

Reviewed-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>