signal.c: fix erroneous syscall kernel-doc

Fix erroneous syscall kernel-doc comments in kernel/signal.c.

Reported-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -2711,8 +2711,8 @@ out:
 /**
  *  sys_rt_sigaction - alter an action taken by a process
  *  @sig: signal to be sent
- *  @act: the thread group ID of the thread
- *  @oact: the PID of the thread
+ *  @act: new sigaction
+ *  @oact: used to save the previous sigaction
  *  @sigsetsize: size of sigset_t type
  */
 SYSCALL_DEFINE4(rt_sigaction, int, sig,