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/include/linux/wl12xx.h b/include/linux/wl12xx.h
index bd70563..95deae3 100644
--- a/include/linux/wl12xx.h
+++ b/include/linux/wl12xx.h
@@ -29,6 +29,7 @@
 	/* SDIO only: IRQ number if WLAN_IRQ line is used, 0 for SDIO IRQs */
 	int irq;
 	bool use_eeprom;
+	int board_ref_clock;
 };
 
 int wl12xx_set_platform_data(const struct wl12xx_platform_data *data);