sfc: Update product naming

We don't use 'Solarstorm' or 'Solarflare Communications' in full
any more.

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