drm/i915: Update PV INFO page definition for Intel GVT-g

Some more definitions in the PV info page are added. They are mainly
for the guest notification to Intel GVT-g device model. They are used
for Broadwell enabling.

The notification of PPGTT page table creation/destroy is to notify
GVT-g device model the life cycle of guest page tables. Then device
model will implement shadow page table for guests.

The notification of context create/destroy is optional. If it is used,
the device model will create/destroy shadow context corresponding to
the context's life cycle. Guest driver needs to make sure that the
context's LRCA and backing storage address unchanged. If it is not
used, the device model will perform the context shadow work in the
context scheduling time.

Signed-off-by: Zhiyuan Lv <zhiyuan.lv@intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>