sfc: Make most filter operations NIC-type-specific

Aside from accelerated RFS, there is almost nothing that can be shared
between the filter table implementations for the Falcon architecture
and EF10.

Move the few shared functions into efx.c and rx.c and the rest into
farch.c.  Introduce efx_nic_type operations for the implementation and
inline wrapper functions that call these.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>