drm/i915/gvt: properly check per_ctx bb valid state

Need to check valid state for per_ctx bb and bypass batch buffer
combine for scan if necessary. Otherwise adding invalid MI batch
buffer start cmd for per_ctx bb will cause scan failure, which is
taken as -EFAULT now so vGPU would be put in failsafe. This trys
to fix that by checking per_ctx bb valid state. Also remove old
invalid WARNING that indirect ctx bb shouldn't depend on valid
per_ctx bb.

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>

drivers/gpu/drm/i915/gvt/scheduler.h

@@ -68,6 +68,7 @@ struct shadow_indirect_ctx {
 struct shadow_per_ctx {
 	unsigned long guest_gma;
 	unsigned long shadow_gma;
+	unsigned valid;
 };
 
 struct intel_shadow_wa_ctx {