draw: remove some dead constant buffer code

draw: remove some dead constant buffer code

Remove the draw_vs_set_constants() and draw_gs_set_constants()
functions and the draw->vs.aligned_constants,
draw->vs.aligned_constant_storage and draw->vs.const_storage_size
fields.  None of it was used.

Reviewed-by: José Fonseca <jfonseca@vmware.com>