intel/eu: Add the RNDU opcode

intel/eu: Add the RNDU opcode

We don't want to use it on gen5 and earlier because only RNDD can be
done with a single instruction and we can implement RNDU(x) as -RNDD(-x)
so it's better to just do that when we have the instruction.  On gen6
and above, we may as well just use the right instruction.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5596>