dm: usb: Drop the EHCI weak functions

These are a pain with driver model because we might have different EHCI
drivers which want to implement them differently. Now that they use
consistent function signatures, we can in good conscience move them to
a struct.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
Fix non-driver-model EHCI to set up the EHCI operations correctly:
Signed-off-by: Tom Rini <trini@konsulko.com>