USB: EHCI: split ehci-omap out to a separate driver

This patch (as1645) converts ehci-omap over to the new "ehci-hcd is a
library" approach, so that it can coexist peacefully with other EHCI
platform drivers and can make use of the private area allocated at
the end of struct ehci_hcd.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>