mtd/nand/sh_flctl: Replace the dangerous mtd_to_flctl macro

The original macro worked only when applied to variables named 'mtd'.
While this could have been fixed by simply renaming the macro argument,
a more type-safe replacement is preferred.
Signed-off-by: NFerenc Wagner <wferi@niif.hu>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

include/linux/mtd/sh_flctl.h

@@ -93,7 +93,10 @@
 #define INIT_FL4ECCRESULT_VAL	0x03FF03FF
 #define LOOP_TIMEOUT_MAX	0x00010000
 
-#define mtd_to_flctl(mtd)	container_of(mtd, struct sh_flctl, mtd)
+static inline struct sh_flctl *mtd_to_flctl(struct mtd_info *mtdinfo)
+{
+	return container_of(mtdinfo, struct sh_flctl, mtd);
+}
 
 struct sh_flctl {
 	struct mtd_info		mtd;