In order to deal with these systems that do not offer HW-based
deactivation of interrupts, let implement a SW-based approach:

- When the irq is queued into a LR, treat it as a pure virtual
  interrupt and set the EOI flag in the LR.

- When the interrupt state is read back from the LR, force a
  deactivation when the state is invalid (neither active nor
  pending)

Interrupts requiring such treatment get the VGIC_SW_RESAMPLE flag.
Signed-off-by: Marc Zyngier <maz@kernel.org>