EHCI : introduce a common ehci_setup

This allow to clean duplicated code in most of SOC driver.

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>  # fixes 3.1 build error
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>