bnxt_en: Add function to calculate Toeplitz hash

For ntuple filters added by aRFS, the Toeplitz hash calculated by our
NIC is available and is used to store the ntuple filter for quick
retrieval.  In the next patches, user defined ntuple filter support
will be added and we need to calculate the same hash for these
filters.  The same hash function needs to be used so we can detect
duplicates.

Add the function bnxt_toeplitz() to calculate the Toeplitz hash for
user defined ntuple filters.  bnxt_toeplitz() uses the same Toeplitz
key and the same key length as the NIC.

bnxt_get_ntp_filter_idx() is added to return the hash index.  For
aRFS, the hash comes from the NIC.  For user defined ntuple, we call
bnxt_toeplitz() to calculate the hash index.

Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Signed-off-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>