kernel: fix new kernel-doc warning in wait.c

Fix new kernel-doc warnings in kernel/wait.c:

  Warning(kernel/wait.c:374): No description found for parameter 'p'
  Warning(kernel/wait.c:374): Excess function parameter 'word' description in 'wake_up_atomic_t'
  Warning(kernel/wait.c:374): Excess function parameter 'bit' description in 'wake_up_atomic_t'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>