radv: don't emit unneeded vertex state.

radv: don't emit unneeded vertex state.

If the number of instances hasn't changed and we've already
emitted it, don't emit it again.

If the vertex shader is the same and the first_instance, vertex_offset
haven't changed don't emit them again.

This increases the fps in GL_vs_VK -t 1 -m -api vk from around 40
to around 60 here, it may not impact anything else.

Dieter also reported smoketest going from 1060->1200 fps.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>