ath79: disable ath79 USB phy drivers by default
We already have an kernel module package "kmod-phy-ath79-usb" to
drive the ath79 USB. It will be selected by the usb base package
"kmod-usb2" and "kmod-usb-ohci".
Signed-off-by: Shiji Yang <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/16380
Signed-off-by: Hauke Mehrtens <[email protected]>