gallium/ttn: minor cleanup
gallium/ttn: minor cleanup

Extract tgsi_dst->Index into a local.. split out from 'gallium/ttn: add
support for temp arrays' for noise reduction..

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

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler