ir_to_mesa: Don't assert that we can't assign matrices. It should work now.

src/mesa/shader/ir_to_mesa.cpp

@@ -1270,7 +1270,6 @@ ir_to_mesa_visitor::visit(ir_assignment *ir)
    struct ir_to_mesa_src_reg r;
    int i;
 
-   assert(!ir->lhs->type->is_matrix());
    assert(!ir->lhs->type->is_array());
    assert(ir->lhs->type->base_type != GLSL_TYPE_STRUCT);