sfc: make capability checking a nic_type function

Various MCDI functions (especially in filter handling) need to check the
 datapath caps, but those live in nic_data (since they don't exist on
 Siena).  Decouple from ef10-specific data structures by adding check_caps
 to the nic_type, to allow using these functions from non-ef10 drivers.

Also add a convenience macro efx_has_cap() to reduce the amount of
 boilerplate involved in calling it.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/siena.c

@@ -948,6 +948,13 @@ fail:
 
 #endif /* CONFIG_SFC_MTD */
 
+unsigned int siena_check_caps(const struct efx_nic *efx,
+			      u8 flag, u32 offset)
+{
+	/* Siena did not support MC_CMD_GET_CAPABILITIES */
+	return 0;
+}
+
 /**************************************************************************
  *
  * Revision-dependent attributes used by efx.c and nic.c