hw/intc/arm_gic: Running priority is group priority, not full priority

hw/intc/arm_gic: Running priority is group priority, not full priority

Priority values for the GIC are divided into a "group priority"
and a "subpriority" (with the division being determined by the
binary point register). The running priority is only determined
by the group priority of the active interrupts, not the
subpriority. In particular, this means that there can't be more
than one active interrupt at any particular group priority.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1438089748-5528-3-git-send-email-peter.maydell@linaro.org