sfc: Add support for Solarflare SFC9100 family

This adds support for the EF10 network controller architecture and the
SFC9100 family, starting with SFC9120 'Farmingdale', and bumps the
driver version to 4.0.

New features in the SFC9100 family include:

- Flexible allocation of internal resources to PCIe physical and virtual
  functions under firmware control
- RX event merging to reduce DMA writes at high packet rates
- Integrated RX timestamping
- PIO buffers for lower TX latency
- Firmware-driven data path that supports additional offload features
  and filter types
- Delivery of packets between functions and to multiple recipients,
  allowing firmware to implement a vswitch
- Multiple RX flow hash (RSS) contexts with their own hash keys and
  indirection tables
- 40G MAC (single port only)

...not all of which are enabled in this initial driver or the initial
firmware release.

Much of the new code is by Jon Cooper.

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