pan/bi: Only delete function temp variables

Other resource variables like UBOs and SSBOs are still useful for
debugging and not harming anything.  Also, some Vulkan-focused passes
look up variables from the otherwise detached resource intrinsics and
use them for things.  We really want to keep them around.

Reviewed-by: Christoph Pillmayer <christoph.pillmayer@arm.com>
Acked-by: Eric R. Smith <eric.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38821>

src/panfrost/compiler/bifrost/bifrost_compile.c

@@ -6251,7 +6251,7 @@ bifrost_preprocess_nir(nir_shader *nir, unsigned gpu_id)
 
    /* Lower away all variables for smaller shaders */
    NIR_PASS(_, nir, nir_lower_vars_to_ssa);
-   NIR_PASS(_, nir, nir_remove_dead_variables, nir_var_all, NULL);
+   NIR_PASS(_, nir, nir_remove_dead_variables, nir_var_function_temp, NULL);
 
    /* We assume that UBO and SSBO were lowered, let's move things around. */
    nir_move_options move_all = nir_move_const_undef | nir_move_load_ubo |