i965: Always do NIR IO lowering at specialization time.

i965: Always do NIR IO lowering at specialization time.

We've now hit literally every case other than geometry shaders (and
compute shaders, but those are a no-op).  So, let's just move geometry
shaders over too and be done with it.

The only advantage to doing this at link time was to save the expense
of running the pass on recompiles.  But we're already running a lot of
passes, and the extra code complexity isn't worth it.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>