nvmem: add NXP LPC18xx OTP driver

Add simple read only driver for the internal OTP (One Time Programmable)
memory found on all NXP LPC18xx and LPC43xx devices.

The OTP memory is split into 4 banks each with 4 32-bits word. Some of
the banks contain predefined data while others are for general purpose
and user programmable via the OTP API in ROM. Note that writing to the
OTP memory is not yet supported.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Tested-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>