futex: Fix kernel-doc comments

futex: Fix kernel-doc comments

Fix those:

  ./kernel/futex/futex.h:208: warning: Function parameter or struct member 'drop_hb_ref' not described in 'futex_q'
  ./kernel/futex/waitwake.c:343: warning: expecting prototype for futex_wait_queue(). Prototype was for futex_do_wait() instead
  ./kernel/futex/waitwake.c:594: warning: Function parameter or struct member 'task' not described in 'futex_wait_setup'

Fixes: 93f1b6d79a73 ("futex: Move futex_queue() into futex_wait_setup()")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250512185641.0450a99b@canb.auug.org.au
Link: https://lore.kernel.org/r/20250515171641.24073-1-bp@kernel.org