anv: Move Create*Pipelines into genX_cmd_buffer.c

anv: Move Create*Pipelines into genX_cmd_buffer.c

Now that we don't have meta, we have no need for a gen-agnostic pipeline
create path.  We can, instead, just generate one Create*Pipelines function
per gen and be done with it.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>