nak/sm70: Don't set a predicate destination on redg

Reduction ops don't return anything, including predicates.  On Turing
through Hopper, this doesn't matter because these bits are ignored.
However, Blackwell uses those bits to adjust address calculations for
reduction ops.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34910>

src/nouveau/compiler/nak/sm70_encode.rs

@@ -3098,6 +3098,7 @@ impl SM70Op for OpAtom {
                     assert!(cmp_src == AtomCmpSrc::Separate);
                     e.set_reg_src(32..40, &self.cmpr);
                     e.set_reg_src(64..72, &self.data);
+                    e.set_pred_dst(81..84, &Dst::None);
                 } else {
                     if e.sm >= 90 && self.atom_type.is_float() {
                         e.set_opcode(0x3a3);
@@ -3106,11 +3107,10 @@ impl SM70Op for OpAtom {
                     }
 
                     e.set_reg_src(32..40, &self.data);
+                    e.set_pred_dst(81..84, &Dst::None);
                     e.set_atom_op(87..91, self.atom_op);
                 }
 
-                e.set_pred_dst(81..84, &Dst::None);
-
                 e.set_field(
                     72..73,
                     match self.mem_space.addr_type() {