glsl: Don't make a name for the function return variable
glsl: Don't make a name for the function return variable

If the name is just going to get dropped, don't bother making it.  If
the name is made, release it sooner (rather than later).

No change Valgrind massif results for a trimmed apitrace of dota2.

Signed-off-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

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