drm/i915/gvt: emulate vgpu engine reset control behavior

drm/i915/gvt: emulate vgpu engine reset control behavior

When SW wishes to reset the render engine, it will program
engine's reset control register and wait response from HW.
We need emulate the behavior of this register so guest i915
driver could walk through the engine reset flow. The registers
are not emulated in gvt yet, this patch add the emulation
logic.

v2: add more desc info in commit message.

Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Du, Changbin <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>