ohci: Rework bus glue integration to allow several at once

The previous model had the module_init & module_exit function in the
bus glue .c files themselves. That's a problem if several glues need
to be selected at once and the driver is built has module. This case
is quite common in embedded system where you want to handle both the
integrated ohci controller and some extra controller on PCI.

The ohci-hcd.c file now provide the module_init & module_exit and
appropriate driver registering/unregistering is done conditionally,
using #ifdefs.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>