mei: fix kernel-doc warnings

Add missed parameters descriptions and return values descriptions

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/misc/mei/hw-txe.h b/drivers/misc/mei/hw-txe.h
index e8dd2d1..ce3ed0b 100644
--- a/drivers/misc/mei/hw-txe.h
+++ b/drivers/misc/mei/hw-txe.h
@@ -40,6 +40,7 @@
  * @mem_addr:            SeC and BRIDGE bars
  * @aliveness:           aliveness (power gating) state of the hardware
  * @readiness:           readiness state of the hardware
+ * @slots:               number of empty slots
  * @wait_aliveness_resp: aliveness wait queue
  * @intr_cause:          translated interrupt cause
  */