MIPS: lantiq: Enable AHB Bus for USB

On Danube and AR9 the USB core is connected though a AHB bus to the main
system cross bar, hence we need to enable the gating clock of the AHB
Bus as well to make the USB controller work.

Fixes: dea54fba ("phy: Add an USB PHY driver for the Lantiq SoCs using the RCU module")
Signed-off-by: Mathias Kresin <dev@kresin.me>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: John Crispin <john@phrozen.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.14+
Patchwork: https://patchwork.linux-mips.org/patch/18814/


Signed-off-by: James Hogan <jhogan@kernel.org>