nvmem: nintendo-otp: Add new driver for the Wii and Wii U OTP

nvmem: nintendo-otp: Add new driver for the Wii and Wii U OTP

This OTP is read-only and contains various keys used by the console to
decrypt, encrypt or verify various pieces of storage.

Its size depends on the console, it is 128 bytes on the Wii and
1024 bytes on the Wii U (split into eight 128 bytes banks).

It can be used directly by writing into one register and reading from
the other one, without any additional synchronisation.

This driver was written based on reversed documentation, see:
https://wiiubrew.org/wiki/Hardware/OTP

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Tested-by: Jonathan Neuschäfer <j.ne@posteo.net>  # on Wii
Tested-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>  # on Wii U
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>