i965/fs: Delete is_last_send(); just check inst->eot.

i965/fs: Delete is_last_send(); just check inst->eot.

This helper function basically just checks inst->eot, but also asserts
that only opcodes we expect to terminate threads have EOT set.  As far
as I'm aware, we've never had such a bug.

Removing it means that we don't have to extend the list for new opcodes.
Cherryview and Skylake introduce an optimization where sampler messages
can have EOT set; scalar GS/HS/DS will likely introduce new opcodes as
well.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>