public/io/netif.h: make control ring hash protocol more general

public/io/netif.h: make control ring hash protocol more general

This patch modified the control ring protocol (of which there is
not yet an implementation) to make it more general. Most of the
concepts are not limited to toeplitz hashing so it's best not to
make them unnecessarily specific.

Apart from changing the names of various definitions and modifying
comments, this patch:

- Adds a new control message type to select a hash algorithm.
- Adds a reference implementation of the toeplitz hash.
- Changes the 'toeplitz' extra info fragment into a 'hash' extra
  info fragment and replaces the octet of padding with the index of
  the algorithm that was used to create the hash value.
- Relaxes the restriction that the mapping table has to be
  power-of-2 sized.

The patch also fixes a few spelling typos noticed along the way.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>