sfc: suppress vadaptor stats when EVB is not present

The raw_mask array is not initialised, so it needs to be
explicitly set to zero in the 'else' branch.

If the EVB capability is not present, a port cannot have multiple
functions so the per-port MAC stats are correct and should match
the corresponding vadaptor stats, so this redundancy can be
removed from the ethtool stats output.

Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>