usb: ohci/uhci - add soft dependencies on ehci_pci

Support for specifying soft dependencies in the modules themselves was
introduced in commit 7cb14ba7.

In Arch we have always been shipping a module.d(5) fragment ordering ohci/uhci
after ehci. If this ordering is really necessary, it would be great to move it
to the kernel and getting the correct fragment generated by depmod.

Signed-off-by: Tom Gundersen <teg@jklm.no>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>