[TESTS] Enable ThumbEE extensions in defconfigs for arm32 guest linux

We have ThumbEE virtualization available in arm32, arm32ve, and arm64
hence enable ThumbEE extensions in linux defconfigs of Realview-PB-A8,
VExpress-A9, and VExpress-A15 guests.

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