clover: Fix regression in module serialization

We need to serialize semantic information for arguments, which was added
in 06139c56fa.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>

src/gallium/state_trackers/clover/core/module.cpp

@@ -157,6 +157,7 @@ namespace {
          _proc(s, x.target_size);
          _proc(s, x.target_align);
          _proc(s, x.ext_type);
+         _proc(s, x.semantic);
       }
    };