drm/nv50: Implement ctxprog/state generation.

This removes dependence on external firmware for NV50 generation cards.
If the generated ctxprogs don't work for you for some reason, please
report it.

Signed-off-by: Marcin Kościelnicki <koriakin@0x04.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>