This adds the EHCI driver back to libpayload and configures
the devicetree to route ports to EHCI.
This is hopefully just temporary until the issues with XHCI
can be worked out.
BUG=chrome-os-partner:23635
BRANCH=rambi
TEST=build and boot from USB on rambi
Change-Id: I0549661f5e5fd83477f4839a05e7e21175b24b64
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/175513