hw/arm/spitz: Use max111x properties to set initial values

Use the new max111x qdev properties to set the initial input
values rather than calling max111x_set_input(); this means that
on system reset the inputs will correctly return to their initial
values.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20200628142429.17111-10-peter.maydell@linaro.org