radv: don't lower vectorized instructions to 32bit

Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15176>

src/amd/vulkan/radv_pipeline.c

@@ -3990,6 +3990,11 @@ lower_bit_size_callback(const nir_instr *instr, void *_)
       return 0;
    nir_alu_instr *alu = nir_instr_as_alu(instr);
 
+   /* If an instruction is not scalarized by this point,
+    * it can be emitted as packed instruction */
+   if (alu->dest.dest.ssa.num_components > 1)
+      return 0;
+
    if (alu->dest.dest.ssa.bit_size & (8 | 16)) {
       unsigned bit_size = alu->dest.dest.ssa.bit_size;
       switch (alu->op) {