ttn: small logic cleanup
ttn: small logic cleanup

The only case where dim!=NULL is where op==load_ubo.  But using
op==load_ubo is less confusing.

Signed-off-by: Rob Clark <6f78cdb10adbe0a7fbbf4098125a51f401c77a5f@freedesktop.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler