sfc: remove ctpio_dmabuf_start from stats

sfc: remove ctpio_dmabuf_start from stats

BugLink: https://bugs.launchpad.net/bugs/1836635
The ctpio_dmabuf_start entry is not actually a stat and shouldn't
be exposed to ethtool.

Fixes: 2c0b6ee837db ("sfc: expose CTPIO stats on NICs that support them")
Signed-off-by: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 458bd99e49742c225f75501591573959c7ef50a2)
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>