USB: ehci-ath79: Add device_id entry for the AR933X SoCs

Also make the USB_EHCI_ATH79 selectable for the AR933X SoCs.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: Kathy Giori <kgiori@qca.qualcomm.com>
Cc: "Luis R.  Rodriguez" <rodrigue@qca.qualcomm.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/2529/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>