MIPS: Loongson64: Fix more __iomem attributes

There are some __iomem type casting being missed in previous patch.
Fix them here.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307020639.QCZOKp8B-lkp@intel.com/Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>