bnxt_en: update RSS config using difference algorithm

Hardware is unable to realize all legal firmware interface state values
for hash_type.  For example, if 4-tuple TCP_IPV4 hash is enabled,
4-tuple UDP_IPV4 hash must also be enabled.  By providing the bits the
user intended to change instead of the possible illegal intermediate
states, the firmware is able to make better compromises when deciding
which bits to ignore.

With this new mechansim, we can now report the actual configured hash
back to the user.  Add bnxt_hwrm_update_rss_hash_cfg() to report the
actual hash after user configuration.

Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>