gm107/ir: add missing NEG modifier for IADD32I

Like FADD32I, the NEG modifier of src0 is at position 56.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: mesa-stable@lists.freedesktop.org

src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp

@@ -1707,6 +1707,7 @@ CodeEmitterGM107::emitIADD()
       emitX  (0x2b);
    } else {
       emitInsn(0x1c000000);
+      emitNEG (0x38, insn->src(0));
       emitSAT (0x36);
       emitX   (0x35);
       emitCC  (0x34);