accel/tcg: Call save_iotlb_data from io_readx as well

Apply save_iotlb_data() to io_readx() as well as to io_writex().
This fixes SEGFAULT on qemu_plugin_hwaddr_phys_addr() call plugins
for addresses inside of MMIO region.

Signed-off-by: Dmitriy Solovev <d.solovev@yadro.com>
Signed-off-by: Mikhail Tyutin <m.tyutin@yadro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230804110903.19968-1-m.tyutin@yadro.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>