nvc0/ir: add support for all the new int64 tgsi opcodes

nvc0/ir: add support for all the new int64 tgsi opcodes

A few thoughts:
 - Some of that LegalizeSSA logic should really live much earlier and be
   subject to the likes of DCE and other useful passes
 - Some of the "lowering" done in from_tgsi should be done later so that
   proper optimization might be done.

However this all works and the above can be improved upon later.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>