drm/i915/wakeref: fix kernel-doc comment

Fix the warning:

drivers/gpu/drm/i915/intel_wakeref.h:118: warning: expecting prototype
for intel_wakeref_get_if_in_use(). Prototype was for
intel_wakeref_get_if_active() instead

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230405104142.766598-2-jani.nikula@intel.com