[EMULATORS] arm_sysregs: Emulate reboot and shutdown using bottom-half

The vmm_manager_guest_reset() and vmm_manager_guest_kick() can be expensive operation hence avoid calling them from Normal VCPU context.

Instead we schedule a work in system workqueue to do vmm_manager_guest_reset() and/or vmm_manager_guest_kick()

Signed-off-by: Anup Patel <anup@brainfault.org>