[ARM] arm32: More improvements to VTLB emulation

This patch does following improvments to VTLB emulation:
1. Simplify VTLB zone configuration macros
2. No need for "ng" field in struct arm_vtlb_entry
3. Use separate function to invalidate TLB entry by VA and ASID

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