VME: Rename vme_slot_get to avoid confusion with reference counting

Traditionally the "get" functions increment the reference count of the
object that is returned, which does not happen with vme_slot_get. The
function vme_slot_get returns the physical VME slot associated with a
particular struct vme_dev. Rename vme_slot_num to avoid any confusion.

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