Allow modular build option for RapidIO subsystem core in MIPS and PowerPC
architectural branches.

At this moment modular RapidIO subsystem build is enabled only for
platforms that use PCI/PCIe based RapidIO controllers (e.g.  Tsi721).
Signed-off-by: NAlexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Jean Delvare <jdelvare@suse.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>