soc/tegra: pmc: Fix unsafe generic_handle_irq() call

In the Linux kernel, the following vulnerability has been resolved: soc/tegra: pmc: Fix unsafe generic_handle_irq() call Currently, when resuming from system suspend on Tegra platforms, the following warning is observed: WARNING: CPU: 0 PID: 14459 at kernel/irq/irqdesc.c:666 Call trace: handle_irq_desc+0x20/0x58 (P) tegra186_pmc_wake_syscore_resume+0xe4/0x15c syscore_resume+0x3c/0xb8 suspend_devices_and_enter+0x510/0x540 pm_suspend+0x16c/0x1d8 The warning occurs because generic_handle_irq() is being called from a non-interrupt context which is considered as unsafe. Fix this warning by deferring generic_handle_irq() call to an IRQ work which gets executed in hard IRQ context where generic_handle_irq() can be called safely. When PREEMPT_RT kernels are used, regular IRQ work (initialized with init_irq_work) is deferred to run in per-CPU kthreads in preemptible context rather than hard IRQ context. Hence, use the IRQ_WORK_INIT_HARD variant so that with PREEMPT_RT kernels, the IRQ work is processed in hardirq context instead of being deferred to a thread which is required for calling generic_handle_irq(). On non-PREEMPT_RT kernels, both init_irq_work() and IRQ_WORK_INIT_HARD() execute in IRQ context, so this change has no functional impact for standard kernel configurations. [treding@nvidia.com: miscellaneous cleanups]