move drivers/mfd/*.h to include/linux/mfd

So drivers like collie_battery driver can use
those files easier.
diff --git a/drivers/mfd/mcp-sa11x0.c b/drivers/mfd/mcp-sa11x0.c
index 62b32da..21218981 100644
--- a/drivers/mfd/mcp-sa11x0.c
+++ b/drivers/mfd/mcp-sa11x0.c
@@ -19,6 +19,7 @@
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/platform_device.h>
+#include <linux/mfd/mcp.h>
 
 #include <mach/dma.h>
 #include <mach/hardware.h>
@@ -28,7 +29,6 @@
 
 #include <mach/assabet.h>
 
-#include "mcp.h"
 
 struct mcp_sa11x0 {
 	u32	mccr0;