Hotplug poweron is not working for boot CPU as it's being
triggerred using PMC and not with Flow Controller. This is
happening because "cpu_powergate_mask" is only getting set
for non-boot CPU's as the boot CPU's first bootup follows
different code path. The patch is marking a CPU as ON within
"cpu_powergate_mask" when turning its power domain on
during power on. This will ensure only first bootup on all
CPU's is using PMC and subsequent hotplug poweron will be
using Flow Controller.