nir: stop adjusting driver location for varying packing

nir: stop adjusting driver location for varying packing

As of 59864e8e020 we just use the location assigned by the front-end and
no longer need this for i965.

Since there were some issues in the logic with assigning arrays the same
driver location if they didn't start at the same location just remove it
and let other drivers implement a solution if needed when they add
ARB_enhanced_layouts support.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>