mtd: char: Drop mtd_mutex usage from mtdchar_open()

It looks unnecessary in the function, remove it from the function
having in mind to remove it completely.
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210217211845.43364-1-alexander.sverdlin@nokia.com

drivers/mtd/mtdchar.c

@@ -58,13 +58,10 @@ static int mtdchar_open(struct inode *inode, struct file *file)
 	if ((file->f_mode & FMODE_WRITE) && (minor & 1))
 		return -EACCES;
 
-	mutex_lock(&mtd_mutex);
 	mtd = get_mtd_device(NULL, devnum);
 
-	if (IS_ERR(mtd)) {
-		ret = PTR_ERR(mtd);
-		goto out;
-	}
+	if (IS_ERR(mtd))
+		return PTR_ERR(mtd);
 
 	if (mtd->type == MTD_ABSENT) {
 		ret = -ENODEV;
@@ -84,13 +81,10 @@ static int mtdchar_open(struct inode *inode, struct file *file)
 	}
 	mfi->mtd = mtd;
 	file->private_data = mfi;
-	mutex_unlock(&mtd_mutex);
 	return 0;
 
 out1:
 	put_mtd_device(mtd);
-out:
-	mutex_unlock(&mtd_mutex);
 	return ret;
 } /* mtdchar_open */