st/mesa: Copy VP TGSI tokens if they exist, even for NIR shaders.

st/mesa: Copy VP TGSI tokens if they exist, even for NIR shaders.

Even if the driver wants to use NIR shaders, we may need to have TGSI
tokens for creating draw module vertex shaders for the feedback/select
render modes.

So...if the st_vertex_program has any TGSI...copy it to the variant.

Acked-by: Eric Anholt <eric@anholt.net>
Tested-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>