sata highbank: add bit-banged SGPIO driver support

Highbank supports SGPIO by bit-banging out the SGPIO signals over
three GPIO pins defined in the DTB. Add support for this SGPIO
functionality.

Signed-off-by: Mark Langsdorf <mark.langsdorf@calxeda.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 05adf29..adfb2df 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -322,6 +322,7 @@
 	u32			em_buf_sz;	/* EM buffer size in byte */
 	u32			em_msg_type;	/* EM message type */
 	struct clk		*clk;		/* Only for platforms supporting clk */
+	void			*plat_data;	/* Other platform data */
 };
 
 extern int ahci_ignore_sss;