net/sfc: support DPDK firmware variant

net/sfc: support DPDK firmware variant

DPDK firmware variant supports equal stride super-buffer Rx mode which
provides higher packet rate and packet marks but requires dedicated
mempool manager with contiguous object block allocation (e.g. bucket).

Also the firmware supports subvariant without checksumming on Tx which
allows to reach higher packet rates on transmit if checksumming is not
required.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Ivan Malov <ivan.malov@oktetlabs.ru>