mtd: Stop updating erase_info->state and calling mtd_erase_callback()

MTD users are no longer checking erase_info->state to determine if the
erase operation failed or succeeded. Moreover, mtd_erase_callback() is
now a NOP.

We can safely get rid of all mtd_erase_callback() calls and all
erase_info->state assignments. While at it, get rid of the
erase_info->state field, all MTD_ERASE_XXX definitions and the
mtd_erase_callback() function.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Bert Kenward <bkenward@solarflare.com>
---
Changes in v2:
- Address a few coding style issues (reported by Miquel)
- Remove comments that are no longer valid (reported by Miquel)
diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
index bb07346..c9e4249 100644
--- a/drivers/mtd/devices/block2mtd.c
+++ b/drivers/mtd/devices/block2mtd.c
@@ -88,17 +88,12 @@ static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
 	size_t len = instr->len;
 	int err;
 
-	instr->state = MTD_ERASING;
 	mutex_lock(&dev->write_mutex);
 	err = _block2mtd_erase(dev, from, len);
 	mutex_unlock(&dev->write_mutex);
-	if (err) {
+	if (err)
 		pr_err("erase failed err = %d\n", err);
-		instr->state = MTD_ERASE_FAILED;
-	} else
-		instr->state = MTD_ERASE_DONE;
 
-	mtd_erase_callback(instr);
 	return err;
 }