ARM: dts: imx7s: enable ocotp

Enable ocotp for i.mx7D/S.
Correct the clock entry and compatible string.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>