[ARM] arm32ve: arm64: Trap and yield when VCPU executes WFE instruction

Just like other hypervisors we trap WFE instruction and yield the
VCPU timeslice so that other things can have a chance to run.

In fact, our arm32 port already traps WFE instruction and yields
on WFE. Some how we had missed this part for arm32ve and arm64
port hence this patch.

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