[ARM] arm32: Add separate VTLB zone for high exception vectors

To make Guest exception handling faster we introduce a dedicated
VTLB zone containing 16 enteries for high exception vectors.

This new VTLB zone improves Guest Linux booting time by 2-3 seconds
and DMIPS when running on QEMU or ARM Fast Models.

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