drm/i915/gvt: Fix workload status after wait

From commit e95433c7, workload status setting
was changed to only capture on error path, but we need to set it properly in
normal path too, otherwise we'll fail to complete workload which could lead
guest VM vGPU reset.

v2: uses braces and add Fixes tag.

Fixes: e95433c7 ("drm/i915: Rearrange i915_wait_request() accounting with callers")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>