nvmem: rockchip-otp: Move read-offset into variant-data

nvmem: rockchip-otp: Move read-offset into variant-data

The RK3588 has an offset into the OTP area where the readable area begins
and automatically adds this to the start address.
Other variants are very much similar to rk3588, just with a different
offset, so move that value into variant-data.

To match the size in bytes, store this value also in bytes and not in
number of blocks.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20250411112251.68002-2-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>