radv: get correct offset into LDS for indexed vars.

This seems more correct to me, since if we have an array
of floats they'll be vec4 aligned, and if we do af[2],
we want the const index to increase by 2 slots in the non
compact case.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105464


Fixes: 94f95919 (radv/ac: add support for TCS/TES inputs/outputs.)
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit f9de2d40)
[Juan A. Suarez: apply patch in ac_nir_to_llvm.c]
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>

Conflicts:
	src/amd/vulkan/radv_nir_to_llvm.c