anv/pipeline: Ralloc prog_data::param of the compile mem_ctx

anv/pipeline: Ralloc prog_data::param of the compile mem_ctx

This way we stop leaking it.  This is completely safe because, when we
hand it off to anv_shader_bin_create or anv_pipeline_cache_upload_kernel,
they make a copy of the entire param array.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>