hw/intc/arm_gic: Fix writes to GICD_ITARGETSRn

hw/intc/arm_gic: Fix writes to GICD_ITARGETSRn

According to the GICv2 specification section 4.3.12, "Interrupt Processor
Targets Registers, GICD_ITARGETSRn":

"Any change to a CPU targets field value:
[...]
* Has an effect on any pending interrupts. This means:
  - adding a CPU interface to the target list of a pending interrupt makes that
    interrupt pending on that CPU interface
  - removing a CPU interface from the target list of a pending interrupt
    removes the pending state of that interrupt on that CPU interface."

Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>
Message-id: 20240524113256.8102-3-sebastian.huber@embedded-brains.de
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>