nvmem: rockchip-efuse: parse 'rockchip,efuse-size'

The eFuse size is defined in property <reg> before, but the length
of registers is not equal to the size on some platforms, so we
add a new property to redefine it.

Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>