intc/arm_gic: Implement virtualization extensions in gic_(deactivate|complete_irq)

intc/arm_gic: Implement virtualization extensions in gic_(deactivate|complete_irq)

Implement virtualization extensions in the gic_deactivate_irq() and
gic_complete_irq() functions.

When the guest writes an invalid vIRQ to V_EOIR or V_DIR, since the
GICv2 specification is not entirely clear here, we adopt the behaviour
observed on real hardware:
  * When V_CTRL.EOIMode is false (EOI split is disabled):
    - In case of an invalid vIRQ write to V_EOIR:
      -> If some bits are set in H_APR, an invalid vIRQ write to V_EOIR
         triggers a priority drop, and increments V_HCR.EOICount.
      -> If V_APR is already cleared, nothing happen

    - An invalid vIRQ write to V_DIR is ignored.

  * When V_CTRL.EOIMode is true:
    - In case of an invalid vIRQ write to V_EOIR:
      -> If some bits are set in H_APR, an invalid vIRQ write to V_EOIR
         triggers a priority drop.
      -> If V_APR is already cleared, nothing happen

    - An invalid vIRQ write to V_DIR increments V_HCR.EOICount.

Signed-off-by: Luc Michel <luc.michel@greensocs.com>
Message-id: 20180727095421.386-13-luc.michel@greensocs.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>