Fix gic_cpu_mask() calculation in ARM GIC

r309616 changed the definition of GICD_ITARGETSR(n) to take the irq
id as argument, but the usage of the macro in gic_cpu_mask() was not
updated to reflect this. This causes the cpu mask to be computed
incorrectly.

Update the GICD_ITARGETSR() call to fix this, this fixes a hang seen
while booting freebsd on qemu-system-aarch64 with SMP enabled.