draw: don't set start_instance and instance id for pt emit

draw: don't set start_instance and instance id for pt emit

This just adds confusion, these parameters are used when fetching vertices
by translate, but certainly not when emitting hw vertices for drivers, they
make no sense there (setting them has no consequences otherwise since there
won't be any elements with instance_divisor set). So just set them to 0 (the
draw_pipe_vbuf code for emitting vertices when the draw pipeline is run
already does exactly that).
Also while here do some whitespace cleanup.

Reviewed-by: Brian Paul <brianp@vmware.com>