[PATCH v2] drm/i915/gvt: move write protect handler out of mmio emulation function

[Zhang, Xiong Y]

> 
> It's a bit confusing that page write protect handler is live in mmio emulation
> handler. This moves it to stand alone gvt ops.
> 
> Also remove unnecessary check of write protected page access in mmio read
> handler and cleanup handling of failsafe case.
> 
> v2: rebase
> 
> Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
[Zhang, Xiong Y] Reviewed-by: XiongZhang