mlxsw: spectrum_acl_bloom_filter: Make mlxsw_sp_acl_bf_key_encode() more flexible

Spectrum-4 will calculate hash function for bloom filter differently from
the existing ASICs.

One of the changes is related to the way that the chunks will be build -
without padding.

As preparation for support of Spectrum-4 bloom filter, make
mlxsw_sp_acl_bf_key_encode() more flexible, so it will be able to use it
for Spectrum-4 as well.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>