bnxt_en: Refactor ntuple filter removal logic in bnxt_cfg_ntp_filters().

Refactor the logic into a new function bnxt_del_ntp_filters().  The
same call will be used when the user deletes an ntuple filter.

The bnxt_hwrm_cfa_ntuple_filter_free() function to call fw to free
the ntuple filter is exported so that the ethtool logic can call it.

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>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>