nvmem: imx-ocotp: remove unused dead code

remove unused dead code

Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>