rapidio: use common destid storage for endpoints and switches

Change code to use one storage location common for switches and endpoints.
This eliminates unnecessary device type checks during basic access
operations.  Logic that assigns destid to RIO devices stays unchanged - as
before, switches use an associated destid because they do not have their
own.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Cc: Thomas Moll <thomas.moll@sysgo.com>
Cc: Micha Nelissen <micha@neli.hopto.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>