block: Convert blk_invalidate_devt() header into a non-kernel-doc header

This patch avoids that the kernel-doc tool warns about this function
header when building with W=1.
Reviewed-by: NChaitanya Kulkarni <chiatanya.kulkarni@wdc.com>
Signed-off-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -532,8 +532,8 @@ void blk_free_devt(dev_t devt)
 	}
 }
 
-/**
- *	We invalidate devt by assigning NULL pointer for devt in idr.
+/*
+ * We invalidate devt by assigning NULL pointer for devt in idr.
  */
 void blk_invalidate_devt(dev_t devt)
 {