CHROMIUM: exynos: dts: do not use external PLL for USB3 on Spring

CHROMIUM: exynos: dts: do not use external PLL for USB3 on Spring

Move the enable gpio configuration for the USB3 PLL to the machine
device tree files, and do not define it on Spring, so the dwc3 driver
assumes that we only use the internal clock.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BUG=chrome-os-partner:16351
TEST=on Spring, plug on usb key on USB3 port and browse the content.

Change-Id: If8f91a34a0cadedada2ad627681a7fe83a6e5c12
Reviewed-on: https://gerrit.chromium.org/gerrit/38685
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Commit-Ready: Vincent Palatin <vpalatin@chromium.org>