i965: Don't consider control flow instructions to have sources.

i965: Don't consider control flow instructions to have sources.

And why did IFF have a destination?

I suspect that once upon a time the disassembler used this information
to know which fields to find the jump targets in. The jump targets have
moved, so the disassembler has to know how to handle these
per-generation anyway.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>