mmc: add led trigger

Add a led trigger for each host controller that indicates if there
is a request active on the controller.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

include/linux/mmc/host.h

@@ -10,6 +10,8 @@
 #ifndef LINUX_MMC_HOST_H
 #define LINUX_MMC_HOST_H
 
+#include <linux/leds.h>
+
 #include <linux/mmc/core.h>
 
 struct mmc_ios {
@@ -133,6 +135,10 @@ struct mmc_host {
 	struct task_struct	*sdio_irq_thread;
 	atomic_t		sdio_irq_thread_abort;
 
+#ifdef CONFIG_LEDS_TRIGGERS
+	struct led_trigger	*led;		/* activity led */
+#endif
+
 	unsigned long		private[0] ____cacheline_aligned;
 };