arm: Rework interrupt affinity management on cell creation

arm: Rework interrupt affinity management on cell creation

So far, we only ensured that the affinities of interrupts given to new
cells match with the corresponding CPU set. However, we also need to
check that Linux properly adjusted the affinity of all its remaining
interrupts properly.

This introduces a new irqchip callback adjust_irq_target which performs
the check and the potential adjustment to the first CPU of a cell on a
per-interrupt basis. A single loop in irqchip_cell_init triggers them.
gic_target_spis and gic_route_spis become obsolete.

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