MIPS: Introduce HAS_RAPIDIO Kconfig option

Introduce the same option as PPC and ARM already have because
RAPIDIO can function in the absence of PCI.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Acked-by: Alexandre Bounine <alex.bou9@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/19987/
Cc: linux-mips@linux-mips.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Matt Porter <mporter@kernel.crashing.org>