usb: ehci: add missing cache managment

Commit 8f62ca64 "usb: ehci: Support interrupt transfers via periodic list"
didn't include any cache management in the new interrupt transfer path.
It also added an extra write to or_asynclistaddr in usb_lowlevel_init(),
without having flushed out the data there.

Add the missing cache management calls, so that the code works again.

This allows the USB keyboard on Tegra's Seaboard/Springbank boards to
work.

Cc: Patrick Georgi <patrick@georgi-clan.de>
Cc: Vincent Palatin <vpalatin@chromium.org>
Cc: Julius Werner <jwerner@chromium.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Stephen Warren <swarren@nvidia.com>