floppy: use del_timer_sync() in init cleanup

When no floppy is found the module code can be released while a timer
function is pending or about to be executed.

CPU0                                  CPU1
				      floppy_init()
timer_softirq()
   spin_lock_irq(&base->lock);
   detach_timer();
   spin_unlock_irq(&base->lock);
   -> Interrupt
					del_timer();
				        return -ENODEV;
                                      module_cleanup();
   <- EOI
   call_timer_fn();
   OOPS

Use del_timer_sync() to prevent this.

Signed-off-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>