USB: EHCI: log a warning if ehci-hcd is not loaded first

This patch (as1139) adds a warning to the system log whenever ehci-hcd
is loaded after ohci-hcd or uhci-hcd.  Nowadays most distributions are
pretty good about not doing this; maybe the warning will help convince
anyone still doing it wrong.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>  [2.6.27]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>