pid can be gotten from uhci device memory in uhci_handle_td(),
so the guest can trigger assert qemu if we get an invalid pid.
And the uhci spec 2.1.2 tells us The Host Controller sets Host
Controller Process Error bit to 1 when it detects a fatal error
and indicates that the Host Controller suffered a consistency
check failure while processing a Transfer Descriptor. An example
of a consistency check failure would be finding an illegal PID
field while processing the packet header portion of the TD.
When this error occurs, the Host Controller clears the Run/Stop
bit in the Command register to prevent further schedule execution.

We'd better to set UHCI_STS_HCPERR and kick an interrupt, check
the pid value at the first of uhci_handle_td function.

https://bugzilla.redhat.com/show_bug.cgi?id=1070027Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Message-id: 1455867238-4720-1-git-send-email-arei.gonglei@huawei.com

[ applied minor codestyle fix ]
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>