Jan Kiszka authored Mar 27, 2019 and Philippe Gerum committed Mar 27, 2019

These steps must be done unconditionally, because if
__ipipe_ack_hrtimer_irq() is called, the tick event will be delivered to
the head domain next, which will neither call ipipe_end() for a tick
event, nor propagate such event to the root stage (at least not using
the same IRQ line).

This plugs a race for timers that are per-CPU but share the same
interrupt number. When setting them up, there is a window where the
first CPU already called ipipe_request_irq, but some other CPU did not
yet ran through grab_timer, thus have ipipe_stolen = 0.

It also solves boot issues with the TSC deadline timer in use.

Based on reasoning provided by Philippe Gerum.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>