mtd: core: handle flashes without OTP gracefully

There are flash drivers which registers the OTP callbacks although the
flash doesn't support OTP regions and return -ENODATA for these
callbacks if there is no OTP. If this happens, the probe of the whole
flash will fail. Fix it by handling the ENODATA return code and skip
the OTP region nvmem setup.

Fixes: 4b361cfa86 ("mtd: core: add OTP nvmem provider support")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210707135359.32398-1-michael@walle.cc

drivers/mtd/mtdcore.c

@@ -806,7 +806,9 @@ static ssize_t mtd_otp_size(struct mtd_info *mtd, bool is_user)
 
 err:
 	kfree(info);
-	return ret;
+
+	/* ENODATA means there is no OTP region. */
+	return ret == -ENODATA ? 0 : ret;
 }
 
 static struct nvmem_device *mtd_otp_nvmem_register(struct mtd_info *mtd,