nvmem: Add DT binding documentation for Vybrid OCOTP driver

Add the devicetree bindings for the Freescale Vybrid On-Chip
OTP driver.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>