nested EPT: fixing wrong handling for L2 guest's direct mmio access

nested EPT: fixing wrong handling for L2 guest's direct mmio access

L2 guest will access the physical device directly(nested VT-d). For such access,
Shadow EPT table should point to device's MMIO. But in current logic, L0 doesn't
distinguish the MMIO whether from qemu or physical device when building shadow EPT table.
This is wrong. This patch will setup the correct shadow EPT table for such MMIO ranges.

Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Acked-by: Tim Deegan <tim@xen.org>