arch: hexagon: kernel: add export symbol function __delay()

Need add __delay() implementation, or can not pass allmodconfig in
next-20131118 tree.

The related error:

    CC      kernel/locking/spinlock_debug.o
  kernel/locking/spinlock_debug.c: In function '__spin_lock_debug':
  kernel/locking/spinlock_debug.c:114:3: error: implicit declaration of function '__delay' [-Werror=implicit-function-declaration]

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Richard Kuo <rkuo@codeaurora.org>

arch/hexagon/kernel/time.c

@@ -229,6 +229,15 @@ void __init time_init(void)
 	late_time_init = time_init_deferred;
 }
 
+void __delay(unsigned long cycles)
+{
+	unsigned long long start = __vmgettime();
+
+	while ((__vmgettime() - start) < cycles)
+		cpu_relax();
+}
+EXPORT_SYMBOL(__delay);
+
 /*
  * This could become parametric or perhaps even computed at run-time,
  * but for now we take the observed simulator jitter.