usb: ehci: rework to take advantage of new lowlevel interface

Kill off ehci-core.h
It was used to specify some static controller data. To support more than
one controller being active at any time we have to carry the controller
data ourselfes. Change the ehci interface accordingly.

NOTE: OMAP implemented the ehci stuff a bit backwards and should be fixed
to do the same thing as other platforms. But the change for now is at least
compile clean.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Reviewed-by: Marek Vasut <marex@denx.de>