Currently all IRQ-tracking state is in task_struct, this means that
task_struct needs to be defined before we use it.

Especially for lockdep_assert_irq*() this can lead to header-hell.

Move the hardirq state into per-cpu variables to avoid the task_struct
dependency.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200623083721.512673481@infradead.org