bus: fsl-mc-bus: fix KASAN use-after-free in fsl_mc_bus_remove()

In the Linux kernel, the following vulnerability has been resolved:

bus: fsl-mc-bus: fix KASAN use-after-free in fsl_mc_bus_remove()

In fsl_mc_bus_remove(), mc->root_mc_bus_dev->mc_io is passed to

fsl_destroy_mc_io(). However, mc->root_mc_bus_dev is already freed in

fsl_mc_device_remove(). Then reference to mc->root_mc_bus_dev->mc_io

triggers KASAN use-after-free. To avoid the use-after-free, keep the

reference to mc->root_mc_bus_dev->mc_io in a local variable and pass to

fsl_destroy_mc_io().

This patch needs rework to apply to kernels older than v5.15.