hw/arm/virt: fix pl011 and pl031 irq flags

hw/arm/virt: fix pl011 and pl031 irq flags

The pl011 and pl031 devices both use level triggered interrupts,
but the device tree we construct was incorrectly telling the
kernel to configure the GIC to treat them as edge triggered.
This meant that output from the pl011 would hang after a while.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1410274423-9461-1-git-send-email-peter.maydell@linaro.org
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Cc: qemu-stable@nongnu.org
(cherry picked from commit 0be969a2d974971628fc4ed95834d22ecf0fd497)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>