USB: musb: JZ4770: Disable vbus power setting for now

It is not working reliably yet and in one case I got an over-current
warning, so to be on the safe side I'm disabling this feature for the
upcoming release.
MIPS: JZ4770: GCW0: defconfig: Disable CPUfreq

The cpufreq driver seems to be unstable on some units; the switches of
frequency appear to trouble the WiFi connection, and crashes may occur
randomly for unknown reasons.