rapidio/rionet: rework driver initialization and removal

Rework probe/remove routines to prevent rionet driver from monopolizing
target RapidIO devices.  Fix conflict with modular RapidIO switch drivers.

Using one of RapidIO messaging channels rionet driver provides a service
layer common to all endpoint devices in a system's RapidIO network.  These
devices may also require their own specific device driver which will be
blocked from attaching to the target device by rionet (or block rionet if
loaded earlier).  To avoid conflict with device-specific drivers, the
rionet driver is reworked to be registered as a subsystem interface on the
RapidIO bus.

The reworked rio_remove_dev() and rionet_exit() routines also include
handling of individual rionet peer device removal which was not supported
before.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andre van Herk <andre.van.herk@Prodrive.nl>
Cc: Micha Nelissen <micha.nelissen@Prodrive.nl>
Cc: Stef van Os <stef.van.os@Prodrive.nl>
Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>