arm64: defconfig: Enable ARM SCMI protocol and drivers

Enable the ARM SCMI protocol and the common clock, cpufreq, reset and
sensors drivers. Broadcom STB platforms (ARCH_BRCMSTB) implement SCMI to
provide support for CPU frequency scaling, clock configuration and
temperature and current sensors.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>