phy: qcom: qmp-usb-legacy: Fix possible NULL-deref on early runtime suspend

In the Linux kernel, the following vulnerability has been resolved: phy: qcom: qmp-usb-legacy: Fix possible NULL-deref on early runtime suspend There is a small window where the runtime suspend callback may run after pm_runtime_enable() and before pm_runtime_forbid(). In this case, a crash occurs because runtime suspend/resume dereferences qmp->phy pointer, which is not yet initialized: `if (!qmp->phy->init_count) {` This can also happen if user re-enables runtime-pm via the sysfs attribute before qmp phy is initialized. Similarly to other qcom phy drivers, introduce a qmp->phy_initialized variable that can be used to avoid relying on the possibly uninitialized phy pointer.