mesa: create program resource hash in a single place

mesa: create program resource hash in a single place

This is a cleanup but also a fix for commit dd09f1d806b. In case of
i965 we did not actually create hash for cached shader programs.

Fixes: dd09f1d806b "mesa/st/i965: add a ProgramResourceHash for quicker resource lookup"
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>