VME: Provide access to VME bus enumeration and fix vme_user match function

The match function for vme_user is completely wrong. It will blindly bind
against the first VME slot on each bus (at this point that would be just the
first bus as the driver can only handle one bus).

The original intention (before some major subsystem changes) was that the
driver bind against the slot to which the bridge was attached in the VME
system and to the bus(es) provided via the "bus" module parameter.

To do this cleanly (i.e. without poking arround in the subsystems internal
stuctures) a functionality has been added to provide access to the bus
enumeration.

Signed-off-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>