nir: Take if uses into account in ssa_def_components_read

Fixes: d800b7daa5 "nir: Add a helper for figuring out what..."
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/compiler/nir/nir.c

@@ -1446,6 +1446,9 @@ nir_ssa_def_components_read(const nir_ssa_def *def)
       }
    }
 
+   if (!list_empty(&def->if_uses))
+      read_mask |= 1;
+
    return read_mask;
 }