i965: Delete linked GLSL IR when using NIR.
This is based on Kenneth's patch to delete 'most of the IR'. Due to linker changes to clone variables, we can now free all of IR. Saves 58MB of memory when replaying a Dota 2 trace on Broadwell. Signed-off-by:Tapani Pälli <tapani.palli@intel.com> Reviewed-by:
Kenneth Graunke <kenneth@whitecape.org> Cc: mesa-stable@lists.freedesktop.org (cherry picked from commit 104c8fc2)