mtd: mtdcore: cleanup mtdcore.h a little

Remove useless extern qualifiers. Not that this is a problem, but we more often
declare function prototypes without 'extern', so this is just about being more
consistent. And I am going to add a couple more prototypes here.

Additionally, remove a useless comment.
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdcore.h

-/* linux/drivers/mtd/mtdcore.h
- *
- * Header file for driver private mtdcore exports
- *
+/*
+ * These are exported solely for the purpose of mtd_blkdevs.c. You
+ * should not use them for _anything_ else.
  */
 
-/* These are exported solely for the purpose of mtd_blkdevs.c. You
-   should not use them for _anything_ else */
-
 extern struct mutex mtd_table_mutex;
-extern struct mtd_info *__mtd_next_device(int i);
 
-extern int add_mtd_device(struct mtd_info *mtd);
-extern int del_mtd_device(struct mtd_info *mtd);
-extern int add_mtd_partitions(struct mtd_info *, const struct mtd_partition *,
-			      int);
-extern int del_mtd_partitions(struct mtd_info *);
-extern int parse_mtd_partitions(struct mtd_info *master,
-				const char * const *types,
-				struct mtd_partition **pparts,
-				struct mtd_part_parser_data *data);
+struct mtd_info *__mtd_next_device(int i);
+int add_mtd_device(struct mtd_info *mtd);
+int del_mtd_device(struct mtd_info *mtd);
+int add_mtd_partitions(struct mtd_info *, const struct mtd_partition *, int);
+int del_mtd_partitions(struct mtd_info *);
+int parse_mtd_partitions(struct mtd_info *master, const char * const *types,
+			 struct mtd_partition **pparts,
+			 struct mtd_part_parser_data *data);
 
 #define mtd_for_each_device(mtd)			\
 	for ((mtd) = __mtd_next_device(0);		\