ata/ahci_platform: Add clock framework support

On many architectures, drivers are supposed to prepare/unprepare &
enable/disable functional clock of device. This patch adds clock support for
ahci_platform.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 6441cbe..9be4712 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -35,6 +35,7 @@
 #ifndef _AHCI_H
 #define _AHCI_H
 
+#include <linux/clk.h>
 #include <linux/libata.h>
 
 /* Enclosure Management Control */
@@ -316,6 +317,7 @@
 	u32 			em_loc; /* enclosure management location */
 	u32			em_buf_sz;	/* EM buffer size in byte */
 	u32			em_msg_type;	/* EM message type */
+	struct clk		*clk;		/* Only for platforms supporting clk */
 };
 
 extern int ahci_ignore_sss;