drm/i915/gvt: Fix the compiling error when CONFIG_DRM_I915_DEBUG_RUNTIME_PM=n

A compiling error was reported when CONFIG_DRM_I915_DEBUG_RUNTIME_PM=n.
Fix the problem by using the pre-defined macro.

Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220427212849.18109-2-zhi.a.wang@intel.com


Reviewed-by: Jani Nikula <jani.nikula@linux.intel.com>