arm64: defconfig: Enable cpufreq for MediaTek

The MediaTek CPUFreq driver provides control of CPU frequency/voltage
on MediaTek SoCs. Since there's no device-tree node to bind it to, the
driver needs to be enabled built-in. Enable it so.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20211217154452.868419-1-nfraprado@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>