FROMLIST: mbox: qcom: replace integer with valid macro

Use the correct macro when registering the platform device.

am link:https://patchwork.kernel.org/patch/10784389/



Co-developed-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Khasim Syed Mohammed <khasim.mohammed@linaro.org>