[ARM] arm32: Halt normal VCPU upon unhandled abort

Currently, we only dump normal VCPU register upon encountering
unhandled abort. This causes infinite prints on the consol
hence hard to debug the actual issue.

This patch halts normal VCPU upon unhandled abort which avoid
infinite prints and helps us debug the issue.

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