radeonsi/gfx10: emit VGT_GS_OUT_PRIM_TYPE from draw and add it to VS_STATE

radeonsi/gfx10: emit VGT_GS_OUT_PRIM_TYPE from draw and add it to VS_STATE

With NGG, the VGT_GS_OUT_PRIM_TYPE can change without a shader change.

The VS_STATE is required for both streamout and culling from a vertex
shader without pre-compiling outprim-specific variants.

We could consider compiling specialized variants in the future. We
could also consider compiling the NGG logic as an epilog.

Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>