rapidio: add modular build option for the subsystem core

Add a configuration option to build RapidIO subsystem core code as a
loadable kernel module.  Currently this option is available only for
x86-based platforms, with the additional patch for PowerPC planned to be
provided later.

This patch replaces kernel command line parameter "riohdid=" with its
module-specific analog "rapidio.hdid=".

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: 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>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 10764a3..2775023 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2259,11 +2259,11 @@
 source "drivers/pci/hotplug/Kconfig"
 
 config RAPIDIO
-	bool "RapidIO support"
+	tristate "RapidIO support"
 	depends on PCI
 	default n
 	help
-	  If you say Y here, the kernel will include drivers and
+	  If enabled this option will include drivers and the core
 	  infrastructure code to support RapidIO interconnect devices.
 
 source "drivers/rapidio/Kconfig"