KVM: ia64: add directed mmio range support for kvm guests

Using vt-d, kvm guests can be assigned physcial devices, so
this patch introduce a new mmio type (directed mmio)
to handle its mmio access.

Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>