sfc: Remove support for SFN4111T, SFT9001 and Falcon GMAC

SFN4111T never reached production and is not being used for internal
or customer testing.

Since we have no production Falcon boards using the SFT9001 or the
GMAC, remove support for them as well.

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