ath79 uses the generic-ehci driver, which does not support regulators
using vbus-supply.

dr_mode is also not useful as the driver does not support multiple
modes.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/17486


Signed-off-by: Robert Marko <robimarko@gmail.com>