nvmem: add Rockchip OTP driver

Newer Rockchip socs like the px30 use a different one-time-programmable
memory controller for things like cpu-id and leakage information,
so add the necessary driver for it.

Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
[ported from vendor 4.4, converted to clock-bulk API and cleanups]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>