hw/cpu/a15mpcore: Correct default value for num-irq

hw/cpu/a15mpcore: Correct default value for num-irq

The a15mpcore device claims that its default value for num-irq
is the number of interrupts used by the A15MP in the vexpress-a15
board. However that chip has 128 external interrupts, not 64.
Since there is only one A15 based model in QEMU currently, we
can fix this by simply changing the default value.

This error was causing recent (3.10) Linux kernels to print
warnings/backtraces when the number of interrupts reported
by the GIC was smaller than an interrupt number they wanted
to use.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1373032481-15280-1-git-send-email-peter.maydell@linaro.org