kthread: switch to new kerneldoc syntax for named variable macro argument

The syntax without dots is available since commit 43756e347f21
("scripts/kernel-doc: Add support for named variable macro arguments").

The same HTML output is produced with and without this patch.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Neuschäfer <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Felix Kuehling <[e-mail]>
Cc: Valentin Schneider <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/kthread.h

···
  * @threadfn: the function to run in the thread
  * @data: data pointer for @threadfn()
  * @namefmt: printf-style format string for the thread name
- * @arg...: arguments for @namefmt.
+ * @arg: arguments for @namefmt.
  *
  * This macro will create a kthread on the current node, leaving it in
  * the stopped state.  This is just a helper for kthread_create_on_node();