arm_gic: gic_update should always update all cores

arm_gic: gic_update should always update all cores

This patch fixes so that gic_update always updates all the cores with
new pending irq states.  If the function returns early it is possible
to get interrupts that has already been acknowledged.

Signed-off-by: Johan Karlsson <johan.karlsson@enea.com>
[PMM: rebased to apply to current master]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>