hw/pci-host/designware: Fix ATU_UPPER_TARGET register access

hw/pci-host/designware: Fix ATU_UPPER_TARGET register access

Fix copy/paste error writing to the ATU_UPPER_TARGET
register, we want to update the upper 32 bits.

Cc: qemu-stable@nongnu.org
Reported-by: Joey <jeundery@gmail.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2861
Fixes: d64e5eabc4c ("pci: Add support for Designware IP block")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Message-Id: <20250331152041.74533-2-philmd@linaro.org>