mailbox: imx: Use devm_pm_runtime_enable()

In the Linux kernel, the following vulnerability has been resolved: mailbox: imx: Use devm_pm_runtime_enable() sashiko complained about early usage of the device while probe isn't completed. This can be mitigated by delaying the pm_runtime_enable() into the removal path instead doing it early. This ensures that in an error case the device is removed (and imx_mu_shutdown()) before pm_runtime_disable() so we don't have to do this manually. For the order to work, lets move devm_mbox_controller_register() until after the pm-runtime part. So the reverse order will be mbox-controller removal followed by disabling pm runtime. Use devm_pm_runtime_enable(), remove manual pm_runtime_disable() invocations and move the pm_runtime handling in probe before devm_mbox_controller_register().

Where it's fixed