ac/nir_to_llvm: fix clamp shadow reference for more hardware

Fixes the following piglit test on my VEGA and matches the behaviour in the
tgsi backend.

tests/spec/glsl-1.10/execution/samplers/glsl-fs-shadow2D-clamp-z.shader_test

Fixes: 625dcbbc ("amd/common: pass address components individually to ac_build_image_intrinsic")

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 5d66f710)