Revert "nir/lower_indirect: Bail early if modes == 0"

"There's no point in walking the program if we're never going to
    actually lower anything."

Except we might lower compacted local arrays.  In that case, modes will
be 0, but there is still lowering to be done.

This reverts commit 7f75cf2a94.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109081
Suggested-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Tested-by: Clayton Craft <clayton.a.craft@intel.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir_lower_indirect_derefs.c

@@ -205,9 +205,6 @@ nir_lower_indirect_derefs(nir_shader *shader, nir_variable_mode modes)
 {
    bool progress = false;
 
-   if (modes == 0)
-      return false;
-
    nir_foreach_function(function, shader) {
       if (function->impl)
          progress = lower_indirects_impl(function->impl, modes) || progress;