glsl: don't eliminate subroutine types.

This stops dead code from removing subroutines types,
we need these for the queries to work properly.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/glsl/opt_dead_code.cpp

@@ -126,6 +126,9 @@ do_dead_code(exec_list *instructions, bool uniform_locations_assigned)
                if (block_type->interface_packing != GLSL_INTERFACE_PACKING_PACKED)
                   continue;
             }
+
+            if (entry->var->type->is_subroutine())
+               continue;
          }
 
 	 entry->var->remove();