posix-timers: Fix nanosleep_copyout() for CONFIG_COMPAT_32BIT_TIME

Commit b5793b0d added support for building the nanosleep compat system
call on 32-bit architectures, but missed one change in nanosleep_copyout(),
which would trigger a BUG() as soon as any architecture is switched over to
use it.

Use the proper config symbol to enable the code path.

Fixes: Commit b5793b0d ("posix-timers: Make compat syscalls depend on CONFIG_COMPAT_32BIT_TIME")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: y2038@lists.linaro.org
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/20180618140811.2998503-1-arnd@arndb.de

kernel/time/hrtimer.c

@@ -1659,7 +1659,7 @@ EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
 int nanosleep_copyout(struct restart_block *restart, struct timespec64 *ts)
 {
 	switch(restart->nanosleep.type) {
-#ifdef CONFIG_COMPAT
+#ifdef CONFIG_COMPAT_32BIT_TIME
 	case TT_COMPAT:
 		if (compat_put_timespec64(ts, restart->nanosleep.compat_rmtp))
 			return -EFAULT;