ARM: dts: imx: change ocotp node name on i.MX6/7 SoCs

Change OCOTP node name from ocotp-ctrl to efuse to be compliant with
yaml schema, it requires the nodename to be one of "eeprom|efuse|nvram".

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>