hw/pci-host/bonito: Move away from old_mmio accessors

Move away from the old_mmio MemoryRegion accessors in the
bonito pci controller.

This device is used only in the MIPS "fulong2e" machine.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180802155147.1863-3-peter.maydell@linaro.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>