i8253: Remove I8253_LOCK config

Now that all extra ifdeffed implementations are gone, depend the lock
export on PCSPKR_PLATFORM

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@arm.linux.org.uk>

drivers/clocksource/i8253.c

@@ -16,7 +16,9 @@
  * 0061-0061 : NMI Control Register which contains two speaker control bits.
  */
 DEFINE_RAW_SPINLOCK(i8253_lock);
+#ifdef CONFIG_PCSPKR_PLATFORM
 EXPORT_SYMBOL(i8253_lock);
+#endif
 
 #ifdef CONFIG_CLKSRC_I8253
 /*