ARM: dts: imx6sl: Use nvmem interface to get fuse data

Although ocotp clock is always ON for i.MX6SL, OCOTP can be
accessed directly, but since i.MX6SL nvmem interface is supported,
and fsl,tempmon-data is deprecated, use it instead of getting fuse
data by reading ocotp directly, this makes all i.MX6 SoCs aligned.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>