hw/intc/arm_gicv3_kvm: Stop wrongly programming GICR_PENDBASER.PTZ bit

hw/intc/arm_gicv3_kvm: Stop wrongly programming GICR_PENDBASER.PTZ bit

If LPIs are disabled, KVM will just ignore the GICR_PENDBASER.PTZ bit when
restoring GICR_CTLR.  Setting PTZ here makes littlt sense in "reduce GIC
initialization time".

And what's worse, PTZ is generally programmed by guest to indicate to the
Redistributor whether the LPI Pending table is zero when enabling LPIs.
If migration is triggered when the PTZ has just been cleared by guest (and
before enabling LPIs), we will see PTZ==1 on the destination side, which
is not as expected.  Let's just drop this hackish userspace behavior.

Also take this chance to refine the comment a bit.

Fixes: 367b9f527bec ("hw/intc/arm_gicv3_kvm: Implement get/put functions")
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Message-id: 20200119133051.642-1-yuzenghui@huawei.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>