rapidio/switches: add driver for IDT gen3 switches

Add RapidIO switch driver for IDT Gen3 switch devices: RXS1632 and
RXS2448.

[alexandre.bounine@idt.com: fixup for original driver patch]
  Link: http://lkml.kernel.org/r/1469137596-18241-1-git-send-email-alexandre.bounine@idt.com
Link: http://lkml.kernel.org/r/1469125134-16523-14-git-send-email-alexandre.bounine@idt.com


Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Tested-by: Barry Wood <barry.wood@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Andre van Herk <andre.van.herk@prodrive-technologies.com>
Cc: Barry Wood <barry.wood@idt.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>