s390/cio: fix kdoc for tiqdio_thinint_handler

Add missing parameter description to fix the following warning:
drivers/s390/cio/qdio_thinint.c:183: warning:
Function parameter or member 'floating' not described in 'tiqdio_thinint_handler'
Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

drivers/s390/cio/qdio_thinint.c

@@ -178,6 +178,7 @@ static inline void tiqdio_call_inq_handlers(struct qdio_irq *irq)
 /**
  * tiqdio_thinint_handler - thin interrupt handler for qdio
  * @airq: pointer to adapter interrupt descriptor
+ * @floating: flag to recognize floating vs. directed interrupts (unused)
  */
 static void tiqdio_thinint_handler(struct airq_struct *airq, bool floating)
 {