[ARM] arm32ve: Ensure that we are booted in HYP-mode only

This patch removes our old methode of switching to HYP-mode in
Xvisor bootup sequence and instead expect that all cores (primary
as well as secondary) will be booted in HYP-mode by bootloader.

Also, this approach comply with Linux KVM ARMv7 bootup flow.

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