sfc: tx ring can only have 2048 entries for all EF10 NICs

Fixes: dd248f1b ("sfc: Add PCI ID for Solarflare 8000 series 10/40G NIC")
Reported-by: Patrick Talbert <ptalbert@redhat.com>
Signed-off-by: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>