tgsi/lowering: don't forget interp for BCOLOR inputs
tgsi/lowering: don't forget interp for BCOLOR inputs

To lower two sided color, tgsi_lowering creates additional BCOLOR inputs
(matching up to the BCOLOR outputs on the vert shader).  These inputs
should copy the interpolation state of their matching COLOR input.

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

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler