hw/misc/applesmc: Simplify DeviceReset handler

hw/misc/applesmc: Simplify DeviceReset handler

Have applesmc_find_key() return a const pointer.
Since the returned buffers are not modified in
applesmc_io_data_write(), it is pointless to
delete and re-add the keys in the DeviceReset
handler. Add them once in DeviceRealize, and
discard them in the DeviceUnrealize handler.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20240410180819.92332-1-philmd@linaro.org>