wait.h: include atomic.h

wait.h: include atomic.h

|  CC      init/main.o
|In file included from include/linux/mmzone.h:9:0,
|                 from include/linux/gfp.h:4,
|                 from include/linux/kmod.h:22,
|                 from include/linux/module.h:13,
|                 from init/main.c:15:
|include/linux/wait.h: In function ‘wait_on_atomic_t’:
|include/linux/wait.h:982:2: error: implicit declaration of function ‘atomic_read’ [-Werror=implicit-function-declaration]
|  if (atomic_read(val) == 0)
|  ^

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>