nir/lower_alu_to_scalar: Don't try to lower unpack_32_2x16

It messes up when trying to lower.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>

src/compiler/nir/nir_lower_alu_to_scalar.c

@@ -194,6 +194,7 @@ lower_alu_instr_scalar(nir_alu_instr *instr, nir_builder *b)
    }
 
    case nir_op_unpack_64_2x32:
+   case nir_op_unpack_32_2x16:
       return false;
 
       LOWER_REDUCTION(nir_op_fdot, nir_op_fmul, nir_op_fadd);