mtd: Get rid of unused fields in struct erase_info

Some fields are not used by MTD drivers, users or core code. Moreover,
those fields are not documented, so get rid of them to avoid any
confusion.

Signed-off-by: Boris Brezillon <[e-mail]>
Reviewed-by: Richard Weinberger <[e-mail]>

include/linux/mtd/mtd.h

···
 	uint64_t addr;
 	uint64_t len;
 	uint64_t fail_addr;
-	u_long time;
-	u_long retries;
-	unsigned dev;
-	unsigned cell;
 	void (*callback) (struct erase_info *self);
 	u_long priv;
 	u_char state;
-	struct erase_info *next;
 };
 
 struct mtd_erase_region_info {