arm64: configs: Enable sun50i cpufreq nvmem

Allwinner H6 needs this driver to be able to get
the correct speed_bin required for DVFS.

Enable this option in arm64 defconfig.

Signed-off-by: Clément Péron <peron.clem@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>