hw/intc/arm_gicv3: ICC_HPPIR* return SPURIOUS if int group is disabled

hw/intc/arm_gicv3: ICC_HPPIR* return SPURIOUS if int group is disabled

If the group of the highest priority pending interrupt is disabled
via ICC_IGRPEN*, the ICC_HPPIR* registers should return
INTID_SPURIOUS, not the interrupt ID.  (See the GIC architecture
specification pseudocode functions ICC_HPPIR1_EL1[] and
HighestPriorityPendingInterrupt().)

Make HPPIR reads honour the group disable, the way we already do
when determining whether to preempt in icc_hppi_can_preempt().

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240328153333.2522667-1-peter.maydell@linaro.org