i965: Port 3DSTATE_VF to genxml and simplify the implementation.

i965: Port 3DSTATE_VF to genxml and simplify the implementation.

The whole "it might be used for non-indexed draws" thing is no longer
true - it turns out this was a mistake, and removed in OpenGL 4.5.
(See Marek's commit 96cbc1ca29e0b1f4f4d6c868b8449999aecb9080.)  So
we can simplify this and just program 0 for non-indexed draws.

We can also use #if blocks to remove the atom on Ivybridge/Baytrail,
now that they have a separate atom list from Haswell.  No more runtime
checks.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>