net/sfc: fix MTU change to check Rx scatter consistency

net/sfc: fix MTU change to check Rx scatter consistency

Rx queue setup function checks configured MTU to make sure that
no oversized packets can be received. But a following call to
set MTU function might make this check irrelevant.

Add a function to check MTU size against Rx buffer size and
additional Rx queue info, including Rx scatter offload.

Fixes: e961cf425e02 ("net/sfc: support MTU change")
Cc: stable@dpdk.org
Signed-off-by: Igor Romanov <igor.romanov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>