wl1271: make ref_clock configurable by board

The wl1271 device is using a reference clock that may change
between board to board.

Make the ref_clock parameter configurable by board settings
instead of having a hard coded value in the sources.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/wl12xx/wl1271.h b/drivers/net/wireless/wl12xx/wl1271.h
index faa5925..4134f44 100644
--- a/drivers/net/wireless/wl12xx/wl1271.h
+++ b/drivers/net/wireless/wl12xx/wl1271.h
@@ -330,6 +330,7 @@
 
 	void (*set_power)(bool enable);
 	int irq;
+	int ref_clock;
 
 	spinlock_t wl_lock;